JDK8中的ConcurrentHashMap源码

2020-01-01 16:06:03来源:博客园 阅读 ()

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JDK8中的ConcurrentHashMap源码

背景

上文JDK8中的HashMap源码写了HashMap,这次写ConcurrentHashMap

ConcurrentHashMap源码

/**
     * Maps the specified key to the specified value in this table.
     * Neither the key nor the value can be null.
     *
     * <p>The value can be retrieved by calling the {@code get} method
     * with a key that is equal to the original key.
     *
     * @param key key with which the specified value is to be associated
     * @param value value to be associated with the specified key
     * @return the previous value associated with {@code key}, or
     *         {@code null} if there was no mapping for {@code key}
     * @throws NullPointerException if the specified key or value is null
     */
    public V put(K key, V value) {
        return putVal(key, value, false);
    }

    /** Implementation for put and putIfAbsent */
    final V putVal(K key, V value, boolean onlyIfAbsent) {
        if (key == null || value == null) throw new NullPointerException();
        int hash = spread(key.hashCode());
        int binCount = 0;
        for (Node<K,V>[] tab = table;;) {
            Node<K,V> f; int n, i, fh;
            //tab为空,则初始化
            if (tab == null || (n = tab.length) == 0)
                tab = initTable();
            else if ((f = tabAt(tab, i = (n - 1) & hash)) == null) { //该槽为空,则尝试插入
                if (casTabAt(tab, i, null,
                             new Node<K,V>(hash, key, value, null)))
                    break;                   // no lock when adding to empty bin
            }
            else if ((fh = f.hash) == MOVED) //正在移动,
                tab = helpTransfer(tab, f);
            else {
                V oldVal = null;
                synchronized (f) { //对该槽进行加锁
                    if (tabAt(tab, i) == f) {
                        if (fh >= 0) {
                            binCount = 1;
                            for (Node<K,V> e = f;; ++binCount) {
                                K ek;
                                if (e.hash == hash &&
                                    ((ek = e.key) == key ||
                                     (ek != null && key.equals(ek)))) {
                                    oldVal = e.val;
                                    if (!onlyIfAbsent)
                                        e.val = value;
                                    break;
                                }
                                Node<K,V> pred = e;
                                if ((e = e.next) == null) {
                                    pred.next = new Node<K,V>(hash, key,
                                                              value, null);
                                    break;
                                }
                            }
                        }
                        else if (f instanceof TreeBin) {
                            Node<K,V> p;
                            binCount = 2;
                            if ((p = ((TreeBin<K,V>)f).putTreeVal(hash, key,
                                                           value)) != null) {
                                oldVal = p.val;
                                if (!onlyIfAbsent)
                                    p.val = value;
                            }
                        }
                    }
                }
                if (binCount != 0) {
                    if (binCount >= TREEIFY_THRESHOLD)
                        treeifyBin(tab, i);
                    if (oldVal != null)
                        return oldVal;
                    break;
                }
            }
        }
        addCount(1L, binCount);
        return null;
    }
/**
     * Returns the value to which the specified key is mapped,
     * or {@code null} if this map contains no mapping for the key.
     *
     * <p>More formally, if this map contains a mapping from a key
     * {@code k} to a value {@code v} such that {@code key.equals(k)},
     * then this method returns {@code v}; otherwise it returns
     * {@code null}.  (There can be at most one such mapping.)
     *
     * @throws NullPointerException if the specified key is null
     */
    public V get(Object key) {
        Node<K,V>[] tab; Node<K,V> e, p; int n, eh; K ek;
        //获得hash值
        int h = spread(key.hashCode());
        //表非空,且该处不为空
        if ((tab = table) != null && (n = tab.length) > 0 &&
            (e = tabAt(tab, (n - 1) & h)) != null) {
            if ((eh = e.hash) == h) { //判断第1个
                if ((ek = e.key) == key || (ek != null && key.equals(ek)))
                    return e.val;
            }
            else if (eh < 0) //eh<0,找其他的
                return (p = e.find(h, key)) != null ? p.val : null;
            while ((e = e.next) != null) { //遍历
                if (e.hash == h &&
                    ((ek = e.key) == key || (ek != null && key.equals(ek))))
                    return e.val;
            }
        }
        return null;
    }

ConcurrentHashMap代码太多了,粘了好几次粘不上来。只粘几个方法吧。

阅后感

ConcurrentHashMap通过几个原子操作尽量减少加锁操作。

扩容部分没有看太明白,尤其时扩容时进行get操作。后续再继续学习。

 

 

 

 

 

/* * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. * * * * * * * * * * * * * * * * * * * * */
/* * * * * * * Written by Doug Lea with assistance from members of JCP JSR-166 * Expert Group and released to the public domain, as explained at * http://creativecommons.org/publicdomain/zero/1.0/ */
package java.util.concurrent;
import java.io.ObjectStreamField;import java.io.Serializable;import java.lang.reflect.ParameterizedType;import java.lang.reflect.Type;import java.util.AbstractMap;import java.util.Arrays;import java.util.Collection;import java.util.Comparator;import java.util.Enumeration;import java.util.HashMap;import java.util.Hashtable;import java.util.Iterator;import java.util.Map;import java.util.NoSuchElementException;import java.util.Set;import java.util.Spliterator;import java.util.concurrent.ConcurrentMap;import java.util.concurrent.ForkJoinPool;import java.util.concurrent.atomic.AtomicReference;import java.util.concurrent.locks.LockSupport;import java.util.concurrent.locks.ReentrantLock;import java.util.function.BiConsumer;import java.util.function.BiFunction;import java.util.function.BinaryOperator;import java.util.function.Consumer;import java.util.function.DoubleBinaryOperator;import java.util.function.Function;import java.util.function.IntBinaryOperator;import java.util.function.LongBinaryOperator;import java.util.function.ToDoubleBiFunction;import java.util.function.ToDoubleFunction;import java.util.function.ToIntBiFunction;import java.util.function.ToIntFunction;import java.util.function.ToLongBiFunction;import java.util.function.ToLongFunction;import java.util.stream.Stream;
/** * A hash table supporting full concurrency of retrievals and * high expected concurrency for updates. This class obeys the * same functional specification as {@link java.util.Hashtable}, and * includes versions of methods corresponding to each method of * {@code Hashtable}. However, even though all operations are * thread-safe, retrieval operations do <em>not</em> entail locking, * and there is <em>not</em> any support for locking the entire table * in a way that prevents all access.  This class is fully * interoperable with {@code Hashtable} in programs that rely on its * thread safety but not on its synchronization details. * * <p>Retrieval operations (including {@code get}) generally do not * block, so may overlap with update operations (including {@code put} * and {@code remove}). Retrievals reflect the results of the most * recently <em>completed</em> update operations holding upon their * onset. (More formally, an update operation for a given key bears a * <em>happens-before</em> relation with any (non-null) retrieval for * that key reporting the updated value.)  For aggregate operations * such as {@code putAll} and {@code clear}, concurrent retrievals may * reflect insertion or removal of only some entries.  Similarly, * Iterators, Spliterators and Enumerations return elements reflecting the * state of the hash table at some point at or since the creation of the * iterator/enumeration.  They do <em>not</em> throw {@link * java.util.ConcurrentModificationException ConcurrentModificationException}. * However, iterators are designed to be used by only one thread at a time. * Bear in mind that the results of aggregate status methods including * {@code size}, {@code isEmpty}, and {@code containsValue} are typically * useful only when a map is not undergoing concurrent updates in other threads. * Otherwise the results of these methods reflect transient states * that may be adequate for monitoring or estimation purposes, but not * for program control. * * <p>The table is dynamically expanded when there are too many * collisions (i.e., keys that have distinct hash codes but fall into * the same slot modulo the table size), with the expected average * effect of maintaining roughly two bins per mapping (corresponding * to a 0.75 load factor threshold for resizing). There may be much * variance around this average as mappings are added and removed, but * overall, this maintains a commonly accepted time/space tradeoff for * hash tables.  However, resizing this or any other kind of hash * table may be a relatively slow operation. When possible, it is a * good idea to provide a size estimate as an optional {@code * initialCapacity} constructor argument. An additional optional * {@code loadFactor} constructor argument provides a further means of * customizing initial table capacity by specifying the table density * to be used in calculating the amount of space to allocate for the * given number of elements.  Also, for compatibility with previous * versions of this class, constructors may optionally specify an * expected {@code concurrencyLevel} as an additional hint for * internal sizing.  Note that using many keys with exactly the same * {@code hashCode()} is a sure way to slow down performance of any * hash table. To ameliorate impact, when keys are {@link Comparable}, * this class may use comparison order among keys to help break ties. * * <p>A {@link Set} projection of a ConcurrentHashMap may be created * (using {@link #newKeySet()} or {@link #newKeySet(int)}), or viewed * (using {@link #keySet(Object)} when only keys are of interest, and the * mapped values are (perhaps transiently) not used or all take the * same mapping value. * * <p>A ConcurrentHashMap can be used as scalable frequency map (a * form of histogram or multiset) by using {@link * java.util.concurrent.atomic.LongAdder} values and initializing via * {@link #computeIfAbsent computeIfAbsent}. For example, to add a count * to a {@code ConcurrentHashMap<String,LongAdder> freqs}, you can use * {@code freqs.computeIfAbsent(k -> new LongAdder()).increment();} * * <p>This class and its views and iterators implement all of the * <em>optional</em> methods of the {@link Map} and {@link Iterator} * interfaces. * * <p>Like {@link Hashtable} but unlike {@link HashMap}, this class * does <em>not</em> allow {@code null} to be used as a key or value. * * <p>ConcurrentHashMaps support a set of sequential and parallel bulk * operations that, unlike most {@link Stream} methods, are designed * to be safely, and often sensibly, applied even with maps that are * being concurrently updated by other threads; for example, when * computing a snapshot summary of the values in a shared registry. * There are three kinds of operation, each with four forms, accepting * functions with Keys, Values, Entries, and (Key, Value) arguments * and/or return values. Because the elements of a ConcurrentHashMap * are not ordered in any particular way, and may be processed in * different orders in different parallel executions, the correctness * of supplied functions should not depend on any ordering, or on any * other objects or values that may transiently change while * computation is in progress; and except for forEach actions, should * ideally be side-effect-free. Bulk operations on {@link java.util.Map.Entry} * objects do not support method {@code setValue}. * * <ul> * <li> forEach: Perform a given action on each element. * A variant form applies a given transformation on each element * before performing the action.</li> * * <li> search: Return the first available non-null result of * applying a given function on each element; skipping further * search when a result is found.</li> * * <li> reduce: Accumulate each element.  The supplied reduction * function cannot rely on ordering (more formally, it should be * both associative and commutative).  There are five variants: * * <ul> * * <li> Plain reductions. (There is not a form of this method for * (key, value) function arguments since there is no corresponding * return type.)</li> * * <li> Mapped reductions that accumulate the results of a given * function applied to each element.</li> * * <li> Reductions to scalar doubles, longs, and ints, using a * given basis value.</li> * * </ul> * </li> * </ul> * * <p>These bulk operations accept a {@code parallelismThreshold} * argument. Methods proceed sequentially if the current map size is * estimated to be less than the given threshold. Using a value of * {@code Long.MAX_VALUE} suppresses all parallelism.  Using a value * of {@code 1} results in maximal parallelism by partitioning into * enough subtasks to fully utilize the {@link * ForkJoinPool#commonPool()} that is used for all parallel * computations. Normally, you would initially choose one of these * extreme values, and then measure performance of using in-between * values that trade off overhead versus throughput. * * <p>The concurrency properties of bulk operations follow * from those of ConcurrentHashMap: Any non-null result returned * from {@code get(key)} and related access methods bears a * happens-before relation with the associated insertion or * update.  The result of any bulk operation reflects the * composition of these per-element relations (but is not * necessarily atomic with respect to the map as a whole unless it * is somehow known to be quiescent).  Conversely, because keys * and values in the map are never null, null serves as a reliable * atomic indicator of the current lack of any result.  To * maintain this property, null serves as an implicit basis for * all non-scalar reduction operations. For the double, long, and * int versions, the basis should be one that, when combined with * any other value, returns that other value (more formally, it * should be the identity element for the reduction). Most common * reductions have these properties; for example, computing a sum * with basis 0 or a minimum with basis MAX_VALUE. * * <p>Search and transformation functions provided as arguments * should similarly return null to indicate the lack of any result * (in which case it is not used). In the case of mapped * reductions, this also enables transformations to serve as * filters, returning null (or, in the case of primitive * specializations, the identity basis) if the element should not * be combined. You can create compound transformations and * filterings by composing them yourself under this "null means * there is nothing there now" rule before using them in search or * reduce operations. * * <p>Methods accepting and/or returning Entry arguments maintain * key-value associations. They may be useful for example when * finding the key for the greatest value. Note that "plain" Entry * arguments can be supplied using {@code new * AbstractMap.SimpleEntry(k,v)}. * * <p>Bulk operations may complete abruptly, throwing an * exception encountered in the application of a supplied * function. Bear in mind when handling such exceptions that other * concurrently executing functions could also have thrown * exceptions, or would have done so if the first exception had * not occurred. * * <p>Speedups for parallel compared to sequential forms are common * but not guaranteed.  Parallel operations involving brief functions * on small maps may execute more slowly than sequential forms if the * underlying work to parallelize the computation is more expensive * than the computation itself.  Similarly, parallelization may not * lead to much actual parallelism if all processors are busy * performing unrelated tasks. * * <p>All arguments to all task methods must be non-null. * * <p>This class is a member of the * <a href="{@docRoot}/../technotes/guides/collections/index.html"> * Java Collections Framework</a>. * * @since 1.5 * @author Doug Lea * @param <K> the type of keys maintained by this map * @param <V> the type of mapped values */public class ConcurrentHashMap<K,V> extends AbstractMap<K,V>    implements ConcurrentMap<K,V>, Serializable {    private static final long serialVersionUID = 7249069246763182397L;
    /*     * Overview:     *     * The primary design goal of this hash table is to maintain     * concurrent readability (typically method get(), but also     * iterators and related methods) while minimizing update     * contention. Secondary goals are to keep space consumption about     * the same or better than java.util.HashMap, and to support high     * initial insertion rates on an empty table by many threads.     *     * This map usually acts as a binned (bucketed) hash table.  Each     * key-value mapping is held in a Node.  Most nodes are instances     * of the basic Node class with hash, key, value, and next     * fields. However, various subclasses exist: TreeNodes are     * arranged in balanced trees, not lists.  TreeBins hold the roots     * of sets of TreeNodes. ForwardingNodes are placed at the heads     * of bins during resizing. ReservationNodes are used as     * placeholders while establishing values in computeIfAbsent and     * related methods.  The types TreeBin, ForwardingNode, and     * ReservationNode do not hold normal user keys, values, or     * hashes, and are readily distinguishable during search etc     * because they have negative hash fields and null key and value     * fields. (These special nodes are either uncommon or transient,     * so the impact of carrying around some unused fields is     * insignificant.)     *     * The table is lazily initialized to a power-of-two size upon the     * first insertion.  Each bin in the table normally contains a     * list of Nodes (most often, the list has only zero or one Node).     * Table accesses require volatile/atomic reads, writes, and     * CASes.  Because there is no other way to arrange this without     * adding further indirections, we use intrinsics     * (sun.misc.Unsafe) operations.     *     * We use the top (sign) bit of Node hash fields for control     * purposes -- it is available anyway because of addressing     * constraints.  Nodes with negative hash fields are specially     * handled or ignored in map methods.     *     * Insertion (via put or its variants) of the first node in an     * empty bin is performed by just CASing it to the bin.  This is     * by far the most common case for put operations under most     * key/hash distributions.  Other update operations (insert,     * delete, and replace) require locks.  We do not want to waste     * the space required to associate a distinct lock object with     * each bin, so instead use the first node of a bin list itself as     * a lock. Locking support for these locks relies on builtin     * "synchronized" monitors.     *     * Using the first node of a list as a lock does not by itself     * suffice though: When a node is locked, any update must first     * validate that it is still the first node after locking it, and     * retry if not. Because new nodes are always appended to lists,     * once a node is first in a bin, it remains first until deleted     * or the bin becomes invalidated (upon resizing).     *     * The main disadvantage of per-bin locks is that other update     * operations on other nodes in a bin list protected by the same     * lock can stall, for example when user equals() or mapping     * functions take a long time.  However, statistically, under     * random hash codes, this is not a common problem.  Ideally, the     * frequency of nodes in bins follows a Poisson distribution     * (http://en.wikipedia.org/wiki/Poisson_distribution) with a     * parameter of about 0.5 on average, given the resizing threshold     * of 0.75, although with a large variance because of resizing     * granularity. Ignoring variance, the expected occurrences of     * list size k are (exp(-0.5) * pow(0.5, k) / factorial(k)). The     * first values are:     *     * 0:    0.60653066     * 1:    0.30326533     * 2:    0.07581633     * 3:    0.01263606     * 4:    0.00157952     * 5:    0.00015795     * 6:    0.00001316     * 7:    0.00000094     * 8:    0.00000006     * more: less than 1 in ten million     *     * Lock contention probability for two threads accessing distinct     * elements is roughly 1 / (8 * #elements) under random hashes.     *     * Actual hash code distributions encountered in practice     * sometimes deviate significantly from uniform randomness.  This     * includes the case when N > (1<<30), so some keys MUST collide.     * Similarly for dumb or hostile usages in which multiple keys are     * designed to have identical hash codes or ones that differs only     * in masked-out high bits. So we use a secondary strategy that     * applies when the number of nodes in a bin exceeds a     * threshold. These TreeBins use a balanced tree to hold nodes (a     * specialized form of red-black trees), bounding search time to     * O(log N).  Each search step in a TreeBin is at least twice as     * slow as in a regular list, but given that N cannot exceed     * (1<<64) (before running out of addresses) this bounds search     * steps, lock hold times, etc, to reasonable constants (roughly     * 100 nodes inspected per operation worst case) so long as keys     * are Comparable (which is very common -- String, Long, etc).     * TreeBin nodes (TreeNodes) also maintain the same "next"     * traversal pointers as regular nodes, so can be traversed in     * iterators in the same way.     *     * The table is resized when occupancy exceeds a percentage     * threshold (nominally, 0.75, but see below).  Any thread     * noticing an overfull bin may assist in resizing after the     * initiating thread allocates and sets up the replacement array.     * However, rather than stalling, these other threads may proceed     * with insertions etc.  The use of TreeBins shields us from the     * worst case effects of overfilling while resizes are in     * progress.  Resizing proceeds by transferring bins, one by one,     * from the table to the next table. However, threads claim small     * blocks of indices to transfer (via field transferIndex) before     * doing so, reducing contention.  A generation stamp in field     * sizeCtl ensures that resizings do not overlap. Because we are     * using power-of-two expansion, the elements from each bin must     * either stay at same index, or move with a power of two     * offset. We eliminate unnecessary node creation by catching     * cases where old nodes can be reused because their next fields     * won't change.  On average, only about one-sixth of them need     * cloning when a table doubles. The nodes they replace will be     * garbage collectable as soon as they are no longer referenced by     * any reader thread that may be in the midst of concurrently     * traversing table.  Upon transfer, the old table bin contains     * only a special forwarding node (with hash field "MOVED") that     * contains the next table as its key. On encountering a     * forwarding node, access and update operations restart, using     * the new table.     *     * Each bin transfer requires its bin lock, which can stall     * waiting for locks while resizing. However, because other     * threads can join in and help resize rather than contend for     * locks, average aggregate waits become shorter as resizing     * progresses.  The transfer operation must also ensure that all     * accessible bins in both the old and new table are usable by any     * traversal.  This is arranged in part by proceeding from the     * last bin (table.length - 1) up towards the first.  Upon seeing     * a forwarding node, traversals (see class Traverser) arrange to     * move to the new table without revisiting nodes.  To ensure that     * no intervening nodes are skipped even when moved out of order,     * a stack (see class TableStack) is created on first encounter of     * a forwarding node during a traversal, to maintain its place if     * later processing the current table. The need for these     * save/restore mechanics is relatively rare, but when one     * forwarding node is encountered, typically many more will be.     * So Traversers use a simple caching scheme to avoid creating so     * many new TableStack nodes. (Thanks to Peter Levart for     * suggesting use of a stack here.)     *     * The traversal scheme also applies to partial traversals of     * ranges of bins (via an alternate Traverser constructor)     * to support partitioned aggregate operations.  Also, read-only     * operations give up if ever forwarded to a null table, which     * provides support for shutdown-style clearing, which is also not     * currently implemented.     *     * Lazy table initialization minimizes footprint until first use,     * and also avoids resizings when the first operation is from a     * putAll, constructor with map argument, or deserialization.     * These cases attempt to override the initial capacity settings,     * but harmlessly fail to take effect in cases of races.     *     * The element count is maintained using a specialization of     * LongAdder. We need to incorporate a specialization rather than     * just use a LongAdder in order to access implicit     * contention-sensing that leads to creation of multiple     * CounterCells.  The counter mechanics avoid contention on     * updates but can encounter cache thrashing if read too     * frequently during concurrent access. To avoid reading so often,     * resizing under contention is attempted only upon adding to a     * bin already holding two or more nodes. Under uniform hash     * distributions, the probability of this occurring at threshold     * is around 13%, meaning that only about 1 in 8 puts check     * threshold (and after resizing, many fewer do so).     *     * TreeBins use a special form of comparison for search and     * related operations (which is the main reason we cannot use     * existing collections such as TreeMaps). TreeBins contain     * Comparable elements, but may contain others, as well as     * elements that are Comparable but not necessarily Comparable for     * the same T, so we cannot invoke compareTo among them. To handle     * this, the tree is ordered primarily by hash value, then by     * Comparable.compareTo order if applicable.  On lookup at a node,     * if elements are not comparable or compare as 0 then both left     * and right children may need to be searched in the case of tied     * hash values. (This corresponds to the full list search that     * would be necessary if all elements were non-Comparable and had     * tied hashes.) On insertion, to keep a total ordering (or as     * close as is required here) across rebalancings, we compare     * classes and identityHashCodes as tie-breakers. The red-black     * balancing code is updated from pre-jdk-collections     * (http://gee.cs.oswego.edu/dl/classes/collections/RBCell.java)     * based in turn on Cormen, Leiserson, and Rivest "Introduction to     * Algorithms" (CLR).     *     * TreeBins also require an additional locking mechanism.  While     * list traversal is always possible by readers even during     * updates, tree traversal is not, mainly because of tree-rotations     * that may change the root node and/or its linkages.  TreeBins     * include a simple read-write lock mechanism parasitic on the     * main bin-synchronization strategy: Structural adjustments     * associated with an insertion or removal are already bin-locked     * (and so cannot conflict with other writers) but must wait for     * ongoing readers to finish. Since there can be only one such     * waiter, we use a simple scheme using a single "waiter" field to     * block writers.  However, readers need never block.  If the root     * lock is held, they proceed along the slow traversal path (via     * next-pointers) until the lock becomes available or the list is     * exhausted, whichever comes first. These cases are not fast, but     * maximize aggregate expected throughput.     *     * Maintaining API and serialization compatibility with previous     * versions of this class introduces several oddities. Mainly: We     * leave untouched but unused constructor arguments refering to     * concurrencyLevel. We accept a loadFactor constructor argument,     * but apply it only to initial table capacity (which is the only     * time that we can guarantee to honor it.) We also declare an     * unused "Segment" class that is instantiated in minimal form     * only when serializing.     *     * Also, solely for compatibility with previous versions of this     * class, it extends AbstractMap, even though all of its methods     * are overridden, so it is just useless baggage.     *     * This file is organized to make things a little easier to follow     * while reading than they might otherwise: First the main static     * declarations and utilities, then fields, then main public     * methods (with a few factorings of multiple public methods into     * internal ones), then sizing methods, trees, traversers, and     * bulk operations.     */
    /* ---------------- Constants -------------- */
    /**     * The largest possible table capacity.  This value must be     * exactly 1<<30 to stay within Java array allocation and indexing     * bounds for power of two table sizes, and is further required     * because the top two bits of 32bit hash fields are used for     * control purposes.     */    private static final int MAXIMUM_CAPACITY = 1 << 30;
    /**     * The default initial table capacity.  Must be a power of 2     * (i.e., at least 1) and at most MAXIMUM_CAPACITY.     */    private static final int DEFAULT_CAPACITY = 16;
    /**     * The largest possible (non-power of two) array size.     * Needed by toArray and related methods.     */    static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
    /**     * The default concurrency level for this table. Unused but     * defined for compatibility with previous versions of this class.     */    private static final int DEFAULT_CONCURRENCY_LEVEL = 16;
    /**     * The load factor for this table. Overrides of this value in     * constructors affect only the initial table capacity.  The     * actual floating point value isn't normally used -- it is     * simpler to use expressions such as {@code n - (n >>> 2)} for     * the associated resizing threshold.     */    private static final float LOAD_FACTOR = 0.75f;
    /**     * The bin count threshold for using a tree rather than list for a     * bin.  Bins are converted to trees when adding an element to a     * bin with at least this many nodes. The value must be greater     * than 2, and should be at least 8 to mesh with assumptions in     * tree removal about conversion back to plain bins upon     * shrinkage.     */    static final int TREEIFY_THRESHOLD = 8;
    /**     * The bin count threshold for untreeifying a (split) bin during a     * resize operation. Should be less than TREEIFY_THRESHOLD, and at     * most 6 to mesh with shrinkage detection under removal.     */    static final int UNTREEIFY_THRESHOLD = 6;
    /**     * The smallest table capacity for which bins may be treeified.     * (Otherwise the table is resized if too many nodes in a bin.)     * The value should be at least 4 * TREEIFY_THRESHOLD to avoid     * conflicts between resizing and treeification thresholds.     */    static final int MIN_TREEIFY_CAPACITY = 64;
    /**     * Minimum number of rebinnings per transfer step. Ranges are     * subdivided to allow multiple resizer threads.  This value     * serves as a lower bound to avoid resizers encountering     * excessive memory contention.  The value should be at least     * DEFAULT_CAPACITY.     */    private static final int MIN_TRANSFER_STRIDE = 16;
    /**     * The number of bits used for generation stamp in sizeCtl.     * Must be at least 6 for 32bit arrays.     */    private static int RESIZE_STAMP_BITS = 16;
    /**     * The maximum number of threads that can help resize.     * Must fit in 32 - RESIZE_STAMP_BITS bits.     */    private static final int MAX_RESIZERS = (1 << (32 - RESIZE_STAMP_BITS)) - 1;
    /**     * The bit shift for recording size stamp in sizeCtl.     */    private static final int RESIZE_STAMP_SHIFT = 32 - RESIZE_STAMP_BITS;
    /*     * Encodings for Node hash fields. See above for explanation.     */    static final int MOVED     = -1; // hash for forwarding nodes    static final int TREEBIN   = -2; // hash for roots of trees    static final int RESERVED  = -3; // hash for transient reservations    static final int HASH_BITS = 0x7fffffff; // usable bits of normal node hash
    /** Number of CPUS, to place bounds on some sizings */    static final int NCPU = Runtime.getRuntime().availableProcessors();
    /** For serialization compatibility. */    private static final ObjectStreamField[] serialPersistentFields = {        new ObjectStreamField("segments", Segment[].class),        new ObjectStreamField("segmentMask", Integer.TYPE),        new ObjectStreamField("segmentShift", Integer.TYPE)    };
    /* ---------------- Nodes -------------- */
    /**     * Key-value entry.  This class is never exported out as a     * user-mutable Map.Entry (i.e., one supporting setValue; see     * MapEntry below), but can be used for read-only traversals used     * in bulk tasks.  Subclasses of Node with a negative hash field     * are special, and contain null keys and values (but are never     * exported).  Otherwise, keys and vals are never null.     */    static class Node<K,V> implements Map.Entry<K,V> {        final int hash;        final K key;        volatile V val;        volatile Node<K,V> next;
        Node(int hash, K key, V val, Node<K,V> next) {            this.hash = hash;            this.key = key;            this.val = val;            this.next = next;        }
        public final K getKey()       { return key; }        public final V getValue()     { return val; }        public final int hashCode()   { return key.hashCode() ^ val.hashCode(); }        public final String toString(){ return key + "=" + val; }        public final V setValue(V value) {            throw new UnsupportedOperationException();        }
        public final boolean equals(Object o) {            Object k, v, u; Map.Entry<?,?> e;            return ((o instanceof Map.Entry) &&                    (k = (e = (Map.Entry<?,?>)o).getKey()) != null &&                    (v = e.getValue()) != null &&                    (k == key || k.equals(key)) &&                    (v == (u = val) || v.equals(u)));        }
        /**         * Virtualized support for map.get(); overridden in subclasses.         */        Node<K,V> find(int h, Object k) {            Node<K,V> e = this;            if (k != null) {                do {                    K ek;                    if (e.hash == h &&                        ((ek = e.key) == k || (ek != null && k.equals(ek))))                        return e;                } while ((e = e.next) != null);            }            return null;        }    }
    /* ---------------- Static utilities -------------- */
    /**     * Spreads (XORs) higher bits of hash to lower and also forces top     * bit to 0. Because the table uses power-of-two masking, sets of     * hashes that vary only in bits above the current mask will     * always collide. (Among known examples are sets of Float keys     * holding consecutive whole numbers in small tables.)  So we     * apply a transform that spreads the impact of higher bits     * downward. There is a tradeoff between speed, utility, and     * quality of bit-spreading. Because many common sets of hashes     * are already reasonably distributed (so don't benefit from     * spreading), and because we use trees to handle large sets of     * collisions in bins, we just XOR some shifted bits in the     * cheapest possible way to reduce systematic lossage, as well as     * to incorporate impact of the highest bits that would otherwise     * never be used in index calculations because of table bounds.     */    static final int spread(int h) {        return (h ^ (h >>> 16)) & HASH_BITS;    }
    /**     * Returns a power of two table size for the given desired capacity.     * See Hackers Delight, sec 3.2     */    private static final int tableSizeFor(int c) {        int n = c - 1;        n |= n >>> 1;        n |= n >>> 2;        n |= n >>> 4;        n |= n >>> 8;        n |= n >>> 16;        return (n < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1;    }
    /**     * Returns x's Class if it is of the form "class C implements     * Comparable<C>", else null.     */    static Class<?> comparableClassFor(Object x) {        if (x instanceof Comparable) {            Class<?> c; Type[] ts, as; Type t; ParameterizedType p;            if ((c = x.getClass()) == String.class) // bypass checks                return c;            if ((ts = c.getGenericInterfaces()) != null) {                for (int i = 0; i < ts.length; ++i) {                    if (((t = ts[i]) instanceof ParameterizedType) &&                        ((p = (ParameterizedType)t).getRawType() ==                         Comparable.class) &&                        (as = p.getActualTypeArguments()) != null &&                        as.length == 1 && as[0] == c) // type arg is c                        return c;                }            }        }        return null;    }
    /**     * Returns k.compareTo(x) if x matches kc (k's screened comparable     * class), else 0.     */    @SuppressWarnings({"rawtypes","unchecked"}) // for cast to Comparable    static int compareComparables(Class<?> kc, Object k, Object x) {        return (x == null || x.getClass() != kc ? 0 :                ((Comparable)k).compareTo(x));    }
    /* ---------------- Table element access -------------- */
    /*     * Volatile access methods are used for table elements as well as     * elements of in-progress next table while resizing.  All uses of     * the tab arguments must be null checked by callers.  All callers     * also paranoically precheck that tab's length is not zero (or an     * equivalent check), thus ensuring that any index argument taking     * the form of a hash value anded with (length - 1) is a valid     * index.  Note that, to be correct wrt arbitrary concurrency     * errors by users, these checks must operate on local variables,     * which accounts for some odd-looking inline assignments below.     * Note that calls to setTabAt always occur within locked regions,     * and so in principle require only release ordering, not     * full volatile semantics, but are currently coded as volatile     * writes to be conservative.     */
    @SuppressWarnings("unchecked")    static final <K,V> Node<K,V> tabAt(Node<K,V>[] tab, int i) {        return (Node<K,V>)U.getObjectVolatile(tab, ((long)i << ASHIFT) + ABASE);    }
    static final <K,V> boolean casTabAt(Node<K,V>[] tab, int i,                                        Node<K,V> c, Node<K,V> v) {        return U.compareAndSwapObject(tab, ((long)i << ASHIFT) + ABASE, c, v);    }
    static final <K,V> void setTabAt(Node<K,V>[] tab, int i, Node<K,V> v) {        U.putObjectVolatile(tab, ((long)i << ASHIFT) + ABASE, v);    }
    /* ---------------- Fields -------------- */
    /**     * The array of bins. Lazily initialized upon first insertion.     * Size is always a power of two. Accessed directly by iterators.     */    transient volatile Node<K,V>[] table;
    /**     * The next table to use; non-null only while resizing.     */    private transient volatile Node<K,V>[] nextTable;
    /**     * Base counter value, used mainly when there is no contention,     * but also as a fallback during table initialization     * races. Updated via CAS.     */    private transient volatile long baseCount;
    /**     * Table initialization and resizing control.  When negative, the     * table is being initialized or resized: -1 for initialization,     * else -(1 + the number of active resizing threads).  Otherwise,     * when table is null, holds the initial table size to use upon     * creation, or 0 for default. After initialization, holds the     * next element count value upon which to resize the table.     */    private transient volatile int sizeCtl;
    /**     * The next table index (plus one) to split while resizing.     */    private transient volatile int transferIndex;
    /**     * Spinlock (locked via CAS) used when resizing and/or creating CounterCells.     */    private transient volatile int cellsBusy;
    /**     * Table of counter cells. When non-null, size is a power of 2.     */    private transient volatile CounterCell[] counterCells;
    // views    private transient KeySetView<K,V> keySet;    private transient ValuesView<K,V> values;    private transient EntrySetView<K,V> entrySet;

    /* ---------------- Public operations -------------- */
    /**     * Creates a new, empty map with the default initial table size (16).     */    public ConcurrentHashMap() {    }
    /**     * Creates a new, empty map with an initial table size     * accommodating the specified number of elements without the need     * to dynamically resize.     *     * @param initialCapacity The implementation performs internal     * sizing to accommodate this many elements.     * @throws IllegalArgumentException if the initial capacity of     * elements is negative     */    public ConcurrentHashMap(int initialCapacity) {        if (initialCapacity < 0)            throw new IllegalArgumentException();        int cap = ((initialCapacity >= (MAXIMUM_CAPACITY >>> 1)) ?                   MAXIMUM_CAPACITY :                   tableSizeFor(initialCapacity + (initialCapacity >>> 1) + 1));        this.sizeCtl = cap;    }
    /**     * Creates a new map with the same mappings as the given map.     *     * @param m the map     */    public ConcurrentHashMap(Map<? extends K, ? extends V> m) {        this.sizeCtl = DEFAULT_CAPACITY;        putAll(m);    }
    /**     * Creates a new, empty map with an initial table size based on     * the given number of elements ({@code initialCapacity}) and     * initial table density ({@code loadFactor}).     *     * @param initialCapacity the initial capacity. The implementation     * performs internal sizing to accommodate this many elements,     * given the specified load factor.     * @param loadFactor the load factor (table density) for     * establishing the initial table size     * @throws IllegalArgumentException if the initial capacity of     * elements is negative or the load factor is nonpositive     *     * @since 1.6     */    public ConcurrentHashMap(int initialCapacity, float loadFactor) {        this(initialCapacity, loadFactor, 1);    }
    /**     * Creates a new, empty map with an initial table size based on     * the given number of elements ({@code initialCapacity}), table     * density ({@code loadFactor}), and number of concurrently     * updating threads ({@code concurrencyLevel}).     *     * @param initialCapacity the initial capacity. The implementation     * performs internal sizing to accommodate this many elements,     * given the specified load factor.     * @param loadFactor the load factor (table density) for     * establishing the initial table size     * @param concurrencyLevel the estimated number of concurrently     * updating threads. The implementation may use this value as     * a sizing hint.     * @throws IllegalArgumentException if the initial capacity is     * negative or the load factor or concurrencyLevel are     * nonpositive     */    public ConcurrentHashMap(int initialCapacity,                             float loadFactor, int concurrencyLevel) {        if (!(loadFactor > 0.0f) || initialCapacity < 0 || concurrencyLevel <= 0)            throw new IllegalArgumentException();        if (initialCapacity < concurrencyLevel)   // Use at least as many bins            initialCapacity = concurrencyLevel;   // as estimated threads        long size = (long)(1.0 + (long)initialCapacity / loadFactor);        int cap = (size >= (long)MAXIMUM_CAPACITY) ?            MAXIMUM_CAPACITY : tableSizeFor((int)size);        this.sizeCtl = cap;    }
    // Original (since JDK1.2) Map methods
    /**     * {@inheritDoc}     */    public int size() {        long n = sumCount();        return ((n < 0L) ? 0 :                (n > (long)Integer.MAX_VALUE) ? Integer.MAX_VALUE :                (int)n);    }
    /**     * {@inheritDoc}     */    public boolean isEmpty() {        return sumCount() <= 0L; // ignore transient negative values    }
    /**     * Returns the value to which the specified key is mapped,     * or {@code null} if this map contains no mapping for the key.     *     * <p>More formally, if this map contains a mapping from a key     * {@code k} to a value {@code v} such that {@code key.equals(k)},     * then this method returns {@code v}; otherwise it returns     * {@code null}.  (There can be at most one such mapping.)     *     * @throws NullPointerException if the specified key is null     */    public V get(Object key) {        Node<K,V>[] tab; Node<K,V> e, p; int n, eh; K ek;        //获得hash值        int h = spread(key.hashCode());        //表非空,且该处不为空        if ((tab = table) != null && (n = tab.length) > 0 &&            (e = tabAt(tab, (n - 1) & h)) != null) {            if ((eh = e.hash) == h) { //判断第1个                if ((ek = e.key) == key || (ek != null && key.equals(ek)))                    return e.val;            }            else if (eh < 0) //eh<0,找其他的                return (p = e.find(h, key)) != null ? p.val : null;            while ((e = e.next) != null) { //遍历                if (e.hash == h &&                    ((ek = e.key) == key || (ek != null && key.equals(ek))))                    return e.val;            }        }        return null;    }
    /**     * Tests if the specified object is a key in this table.     *     * @param  key possible key     * @return {@code true} if and only if the specified object     *         is a key in this table, as determined by the     *         {@code equals} method; {@code false} otherwise     * @throws NullPointerException if the specified key is null     */    public boolean containsKey(Object key) {        return get(key) != null;    }
    /**     * Returns {@code true} if this map maps one or more keys to the     * specified value. Note: This method may require a full traversal     * of the map, and is much slower than method {@code containsKey}.     *     * @param value value whose presence in this map is to be tested     * @return {@code true} if this map maps one or more keys to the     *         specified value     * @throws NullPointerException if the specified value is null     */    public boolean containsValue(Object value) {        if (value == null)            throw new NullPointerException();        Node<K,V>[] t;        if ((t = table) != null) {            Traverser<K,V> it = new Traverser<K,V>(t, t.length, 0, t.length);            for (Node<K,V> p; (p = it.advance()) != null; ) {                V v;                if ((v = p.val) == value || (v != null && value.equals(v)))                    return true;            }        }        return false;    }
    /**     * Maps the specified key to the specified value in this table.     * Neither the key nor the value can be null.     *     * <p>The value can be retrieved by calling the {@code get} method     * with a key that is equal to the original key.     *     * @param key key with which the specified value is to be associated     * @param value value to be associated with the specified key     * @return the previous value associated with {@code key}, or     *         {@code null} if there was no mapping for {@code key}     * @throws NullPointerException if the specified key or value is null     */    public V put(K key, V value) {        return putVal(key, value, false);    }
    /** Implementation for put and putIfAbsent */    final V putVal(K key, V value, boolean onlyIfAbsent) {        if (key == null || value == null) throw new NullPointerException();        int hash = spread(key.hashCode());        int binCount = 0;        for (Node<K,V>[] tab = table;;) {            Node<K,V> f; int n, i, fh;            //tab为空,则初始化            if (tab == null || (n = tab.length) == 0)                tab = initTable();            else if ((f = tabAt(tab, i = (n - 1) & hash)) == null) { //该槽为空,则尝试插入                if (casTabAt(tab, i, null,                             new Node<K,V>(hash, key, value, null)))                    break;                   // no lock when adding to empty bin            }            else if ((fh = f.hash) == MOVED) //正在移动,                tab = helpTransfer(tab, f);            else {                V oldVal = null;                synchronized (f) { //对该槽进行加锁                    if (tabAt(tab, i) == f) {                        if (fh >= 0) {                            binCount = 1;                            for (Node<K,V> e = f;; ++binCount) {                                K ek;                                if (e.hash == hash &&                                    ((ek = e.key) == key ||                                     (ek != null && key.equals(ek)))) {                                    oldVal = e.val;                                    if (!onlyIfAbsent)                                        e.val = value;                                    break;                                }                                Node<K,V> pred = e;                                if ((e = e.next) == null) {                                    pred.next = new Node<K,V>(hash, key,                                                              value, null);                                    break;                                }                            }                        }                        else if (f instanceof TreeBin) {                            Node<K,V> p;                            binCount = 2;                            if ((p = ((TreeBin<K,V>)f).putTreeVal(hash, key,                                                           value)) != null) {                                oldVal = p.val;                                if (!onlyIfAbsent)                                    p.val = value;                            }                        }                    }                }                if (binCount != 0) {                    if (binCount >= TREEIFY_THRESHOLD)                        treeifyBin(tab, i);                    if (oldVal != null)                        return oldVal;                    break;                }            }        }        addCount(1L, binCount);        return null;    }
    /**     * Copies all of the mappings from the specified map to this one.     * These mappings replace any mappings that this map had for any of the     * keys currently in the specified map.     *     * @param m mappings to be stored in this map     */    public void putAll(Map<? extends K, ? extends V> m) {        tryPresize(m.size());        for (Map.Entry<? extends K, ? extends V> e : m.entrySet())            putVal(e.getKey(), e.getValue(), false);    }
    /**     * Removes the key (and its corresponding value) from this map.     * This method does nothing if the key is not in the map.     *     * @param  key the key that needs to be removed     * @return the previous value associated with {@code key}, or     *         {@code null} if there was no mapping for {@code key}     * @throws NullPointerException if the specified key is null     */    public V remove(Object key) {        return replaceNode(key, null, null);    }
    /**     * Implementation for the four public remove/replace methods:     * Replaces node value with v, conditional upon match of cv if     * non-null.  If resulting value is null, delete.     */    final V replaceNode(Object key, V value, Object cv) {        int hash = spread(key.hashCode());        for (Node<K,V>[] tab = table;;) {            Node<K,V> f; int n, i, fh;            if (tab == null || (n = tab.length) == 0 ||                (f = tabAt(tab, i = (n - 1) & hash)) == null)                break;            else if ((fh = f.hash) == MOVED)                tab = helpTransfer(tab, f);            else {                V oldVal = null;                boolean validated = false;                synchronized (f) {                    if (tabAt(tab, i) == f) {                        if (fh >= 0) {                            validated = true;                            for (Node<K,V> e = f, pred = null;;) {                                K ek;                                if (e.hash == hash &&                                    ((ek = e.key) == key ||                                     (ek != null && key.equals(ek)))) {                                    V ev = e.val;                                    if (cv == null || cv == ev ||                                        (ev != null && cv.equals(ev))) {                                        oldVal = ev;                                        if (value != null)                                            e.val = value;                                        else if (pred != null)                                            pred.next = e.next;                                        else                                            setTabAt(tab, i, e.next);                                    }                                    break;                                }                                pred = e;                                if ((e = e.next) == null)                                    break;                            }                        }                        else if (f instanceof TreeBin) {                            validated = true;                            TreeBin<K,V> t = (TreeBin<K,V>)f;                            TreeNode<K,V> r, p;                            if ((r = t.root) != null &&                                (p = r.findTreeNode(hash, key, null)) != null) {                                V pv = p.val;                                if (cv == null || cv == pv ||                                    (pv != null && cv.equals(pv))) {                                    oldVal = pv;                                    if (value != null)                                        p.val = value;                                    else if (t.removeTreeNode(p))                                        setTabAt(tab, i, untreeify(t.first));                                }                            }                        }                    }                }                if (validated) {                    if (oldVal != null) {                        if (value == null)                            addCount(-1L, -1);                        return oldVal;                    }                    break;                }            }        }        return null;    }
    /**     * Removes all of the mappings from this map.     */    public void clear() {        long delta = 0L; // negative number of deletions        int i = 0;        Node<K,V>[] tab = table;        while (tab != null && i < tab.length) {            int fh;            Node<K,V> f = tabAt(tab, i);            if (f == null)                ++i;            else if ((fh = f.hash) == MOVED) {                tab = helpTransfer(tab, f);                i = 0; // restart            }            else {                synchronized (f) {                    if (tabAt(tab, i) == f) {                        Node<K,V> p = (fh >= 0 ? f :                                       (f instanceof TreeBin) ?                                       ((TreeBin<K,V>)f).first : null);                        while (p != null) {                            --delta;                            p = p.next;                        }                        setTabAt(tab, i++, null);                    }                }            }        }        if (delta != 0L)            addCount(delta, -1);    }
    /**     * Returns a {@link Set} view of the keys contained in this map.     * The set is backed by the map, so changes to the map are     * reflected in the set, and vice-versa. The set supports element     * removal, which removes the corresponding mapping from this map,     * via the {@code Iterator.remove}, {@code Set.remove},     * {@code removeAll}, {@code retainAll}, and {@code clear}     * operations.  It does not support the {@code add} or     * {@code addAll} operations.     *     * <p>The view's iterators and spliterators are     * <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>.     *     * <p>The view's {@code spliterator} reports {@link Spliterator#CONCURRENT},     * {@link Spliterator#DISTINCT}, and {@link Spliterator#NONNULL}.     *     * @return the set view     */    public KeySetView<K,V> keySet() {        KeySetView<K,V> ks;        return (ks = keySet) != null ? ks : (keySet = new KeySetView<K,V>(this, null));    }
    /**     * Returns a {@link Collection} view of the values contained in this map.     * The collection is backed by the map, so changes to the map are     * reflected in the collection, and vice-versa.  The collection     * supports element removal, which removes the corresponding     * mapping from this map, via the {@code Iterator.remove},     * {@code Collection.remove}, {@code removeAll},     * {@code retainAll}, and {@code clear} operations.  It does not     * support the {@code add} or {@code addAll} operations.     *     * <p>The view's iterators and spliterators are     * <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>.     *     * <p>The view's {@code spliterator} reports {@link Spliterator#CONCURRENT}     * and {@link Spliterator#NONNULL}.     *     * @return the collection view     */    public Collection<V> values() {        ValuesView<K,V> vs;        return (vs = values) != null ? vs : (values = new ValuesView<K,V>(this));    }
    /**     * Returns a {@link Set} view of the mappings contained in this map.     * The set is backed by the map, so changes to the map are     * reflected in the set, and vice-versa.  The set supports element     * removal, which removes the corresponding mapping from the map,     * via the {@code Iterator.remove}, {@code Set.remove},     * {@code removeAll}, {@code retainAll}, and {@code clear}     * operations.     *     * <p>The view's iterators and spliterators are     * <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>.     *     * <p>The view's {@code spliterator} reports {@link Spliterator#CONCURRENT},     * {@link Spliterator#DISTINCT}, and {@link Spliterator#NONNULL}.     *     * @return the set view     */    public Set<Map.Entry<K,V>> entrySet() {        EntrySetView<K,V> es;        return (es = entrySet) != null ? es : (entrySet = new EntrySetView<K,V>(this));    }
    /**     * Returns the hash code value for this {@link Map}, i.e.,     * the sum of, for each key-value pair in the map,     * {@code key.hashCode() ^ value.hashCode()}.     *     * @return the hash code value for this map     */    public int hashCode() {        int h = 0;        Node<K,V>[] t;        if ((t = table) != null) {            Traverser<K,V> it = new Traverser<K,V>(t, t.length, 0, t.length);            for (Node<K,V> p; (p = it.advance()) != null; )                h += p.key.hashCode() ^ p.val.hashCode();        }        return h;    }
    /**     * Returns a string representation of this map.  The string     * representation consists of a list of key-value mappings (in no     * particular order) enclosed in braces ("{@code {}}").  Adjacent     * mappings are separated by the characters {@code ", "} (comma     * and space).  Each key-value mapping is rendered as the key     * followed by an equals sign ("{@code =}") followed by the     * associated value.     *     * @return a string representation of this map     */    public String toString() {        Node<K,V>[] t;        int f = (t = table) == null ? 0 : t.length;        Traverser<K,V> it = new Traverser<K,V>(t, f, 0, f);        StringBuilder sb = new StringBuilder();        sb.append('{');        Node<K,V> p;        if ((p = it.advance()) != null) {            for (;;) {                K k = p.key;                V v = p.val;                sb.append(k == this ? "(this Map)" : k);                sb.append('=');                sb.append(v == this ? "(this Map)" : v);                if ((p = it.advance()) == null)                    break;                sb.append(',').append(' ');            }        }        return sb.append('}').toString();    }
    /**     * Compares the specified object with this map for equality.     * Returns {@code true} if the given object is a map with the same     * mappings as this map.  This operation may return misleading     * results if either map is concurrently modified during execution     * of this method.     *     * @param o object to be compared for equality with this map     * @return {@code true} if the specified object is equal to this map     */    public boolean equals(Object o) {        if (o != this) {            if (!(o instanceof Map))                return false;            Map<?,?> m = (Map<?,?>) o;            Node<K,V>[] t;            int f = (t = table) == null ? 0 : t.length;            Traverser<K,V> it = new Traverser<K,V>(t, f, 0, f);            for (Node<K,V> p; (p = it.advance()) != null; ) {                V val = p.val;                Object v = m.get(p.key);                if (v == null || (v != val && !v.equals(val)))                    return false;            }            for (Map.Entry<?,?> e : m.entrySet()) {                Object mk, mv, v;                if ((mk = e.getKey()) == null ||                    (mv = e.getValue()) == null ||                    (v = get(mk)) == null ||                    (mv != v && !mv.equals(v)))                    return false;            }        }        return true;    }
    /**     * Stripped-down version of helper class used in previous version,     * declared for the sake of serialization compatibility     */    static class Segment<K,V> extends ReentrantLock implements Serializable {        private static final long serialVersionUID = 2249069246763182397L;        final float loadFactor;        Segment(float lf) { this.loadFactor = lf; }    }
    /**     * Saves the state of the {@code ConcurrentHashMap} instance to a     * stream (i.e., serializes it).     * @param s the stream     * @throws java.io.IOException if an I/O error occurs     * @serialData     * the key (Object) and value (Object)     * for each key-value mapping, followed by a null pair.     * The key-value mappings are emitted in no particular order.     */    private void writeObject(java.io.ObjectOutputStream s)        throws java.io.IOException {        // For serialization compatibility        // Emulate segment calculation from previous version of this class        int sshift = 0;        int ssize = 1;        while (ssize < DEFAULT_CONCURRENCY_LEVEL) {            ++sshift;            ssize <<= 1;        }        int segmentShift = 32 - sshift;        int segmentMask = ssize - 1;        @SuppressWarnings("unchecked")        Segment<K,V>[] segments = (Segment<K,V>[])            new Segment<?,?>[DEFAULT_CONCURRENCY_LEVEL];        for (int i = 0; i < segments.length; ++i)            segments[i] = new Segment<K,V>(LOAD_FACTOR);        s.putFields().put("segments", segments);        s.putFields().put("segmentShift", segmentShift);        s.putFields().put("segmentMask", segmentMask);        s.writeFields();
        Node<K,V>[] t;        if ((t = table) != null) {            Traverser<K,V> it = new Traverser<K,V>(t, t.length, 0, t.length);            for (Node<K,V> p; (p = it.advance()) != null; ) {                s.writeObject(p.key);                s.writeObject(p.val);            }        }        s.writeObject(null);        s.writeObject(null);        segments = null; // throw away    }
    /**     * Reconstitutes the instance from a stream (that is, deserializes it).     * @param s the stream     * @throws ClassNotFoundException if the class of a serialized object     *         could not be found     * @throws java.io.IOException if an I/O error occurs     */    private void readObject(java.io.ObjectInputStream s)        throws java.io.IOException, ClassNotFoundException {        /*         * To improve performance in typical cases, we create nodes         * while reading, then place in table once size is known.         * However, we must also validate uniqueness and deal with         * overpopulated bins while doing so, which requires         * specialized versions of putVal mechanics.         */        sizeCtl = -1; // force exclusion for table construction        s.defaultReadObject();        long size = 0L;        Node<K,V> p = null;        for (;;) {            @SuppressWarnings("unchecked")            K k = (K) s.readObject();            @SuppressWarnings("unchecked")            V v = (V) s.readObject();            if (k != null && v != null) {                p = new Node<K,V>(spread(k.hashCode()), k, v, p);                ++size;            }            else                break;        }        if (size == 0L)            sizeCtl = 0;        else {            int n;            if (size >= (long)(MAXIMUM_CAPACITY >>> 1))                n = MAXIMUM_CAPACITY;            else {                int sz = (int)size;                n = tableSizeFor(sz + (sz >>> 1) + 1);            }            @SuppressWarnings("unchecked")            Node<K,V>[] tab = (Node<K,V>[])new Node<?,?>[n];            int mask = n - 1;            long added = 0L;            while (p != null) {                boolean insertAtFront;                Node<K,V> next = p.next, first;                int h = p.hash, j = h & mask;                if ((first = tabAt(tab, j)) == null)                    insertAtFront = true;                else {                    K k = p.key;                    if (first.hash < 0) {                        TreeBin<K,V> t = (TreeBin<K,V>)first;                        if (t.putTreeVal(h, k, p.val) == null)                            ++added;                        insertAtFront = false;                    }                    else {                        int binCount = 0;                        insertAtFront = true;                        Node<K,V> q; K qk;                        for (q = first; q != null; q = q.next) {                            if (q.hash == h &&                                ((qk = q.key) == k ||                                 (qk != null && k.equals(qk)))) {                                insertAtFront = false;                                break;                            }                            ++binCount;                        }                        if (insertAtFront && binCount >= TREEIFY_THRESHOLD) {                            insertAtFront = false;                            ++added;                            p.next = first;                            TreeNode<K,V> hd = null, tl = null;                            for (q = p; q != null; q = q.next) {                                TreeNode<K,V> t = new TreeNode<K,V>                                    (q.hash, q.key, q.val, null, null);                                if ((t.prev = tl) == null)                                    hd = t;                                else                                    tl.next = t;                                tl = t;                            }                            setTabAt(tab, j, new TreeBin<K,V>(hd));                        }                    }                }                if (insertAtFront) {                    ++added;                    p.next = first;                    setTabAt(tab, j, p);                }                p = next;            }            table = tab;            sizeCtl = n - (n >>> 2);            baseCount = added;        }    }
    // ConcurrentMap methods
    /**     * {@inheritDoc}     *     * @return the previous value associated with the specified key,     *         or {@code null} if there was no mapping for the key     * @throws NullPointerException if the specified key or value is null     */    public V putIfAbsent(K key, V value) {        return putVal(key, value, true);    }
    /**     * {@inheritDoc}     *     * @throws NullPointerException if the specified key is null     */    public boolean remove(Object key, Object value) {        if (key == null)            throw new NullPointerException();        return value != null && replaceNode(key, null, value) != null;    }
    /**     * {@inheritDoc}     *     * @throws NullPointerException if any of the arguments are null     */    public boolean replace(K key, V oldValue, V newValue) {        if (key == null || oldValue == null || newValue == null)            throw new NullPointerException();        return replaceNode(key, newValue, oldValue) != null;    }
    /**     * {@inheritDoc}     *     * @return the previous value associated with the specified key,     *         or {@code null} if there was no mapping for the key     * @throws NullPointerException if the specified key or value is null     */    public V replace(K key, V value) {        if (key == null || value == null)            throw new NullPointerException();        return replaceNode(key, value, null);    }
    // Overrides of JDK8+ Map extension method defaults
    /**     * Returns the value to which the specified key is mapped, or the     * given default value if this map contains no mapping for the     * key.     *     * @param key the key whose associated value is to be returned     * @param defaultValue the value to return if this map contains     * no mapping for the given key     * @return the mapping for the key, if present; else the default value     * @throws NullPointerException if the specified key is null     */    public V getOrDefault(Object key, V defaultValue) {        V v;        return (v = get(key)) == null ? defaultValue : v;    }
    public void forEach(BiConsumer<? super K, ? super V> action) {        if (action == null) throw new NullPointerException();        Node<K,V>[] t;        if ((t = table) != null) {            Traverser<K,V> it = new Traverser<K,V>(t, t.length, 0, t.length);            for (Node<K,V> p; (p = it.advance()) != null; ) {                action.accept(p.key, p.val);            }        }    }
    public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {        if (function == null) throw new NullPointerException();        Node<K,V>[] t;        if ((t = table) != null) {            Traverser<K,V> it = new Traverser<K,V>(t, t.length, 0, t.length);            for (Node<K,V> p; (p = it.advance()) != null; ) {                V oldValue = p.val;                for (K key = p.key;;) {                    V newValue = function.apply(key, oldValue);                    if (newValue == null)                        throw new NullPointerException();                    if (replaceNode(key, newValue, oldValue) != null ||                        (oldValue = get(key)) == null)                        break;                }            }        }    }
    /**     * If the specified key is not already associated with a value,     * attempts to compute its value using the given mapping function     * and enters it into this map unless {@code null}.  The entire     * method invocation is performed atomically, so the function is     * applied at most once per key.  Some attempted update operations     * on this map by other threads may be blocked while computation     * is in progress, so the computation should be short and simple,     * and must not attempt to update any other mappings of this map.     *     * @param key key with which the specified value is to be associated     * @param mappingFunction the function to compute a value     * @return the current (existing or computed) value associated with     *         the specified key, or null if the computed value is null     * @throws NullPointerException if the specified key or mappingFunction     *         is null     * @throws IllegalStateException if the computation detectably     *         attempts a recursive update to this map that would     *         otherwise never complete     * @throws RuntimeException or Error if the mappingFunction does so,     *         in which case the mapping is left unestablished     */    public V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) {        if (key == null || mappingFunction == null)            throw new NullPointerException();        int h = spread(key.hashCode());        V val = null;        int binCount = 0;        for (Node<K,V>[] tab = table;;) {            Node<K,V> f; int n, i, fh;            if (tab == null || (n = tab.length) == 0)                tab = initTable();            else if ((f = tabAt(tab, i = (n - 1) & h)) == null) {                Node<K,V> r = new ReservationNode<K,V>();                synchronized (r) {                    if (casTabAt(tab, i, null, r)) {                        binCount = 1;                        Node<K,V> node = null;                        try {                            if ((val = mappingFunction.apply(key)) != null)                                node = new Node<K,V>(h, key, val, null);                        } finally {                            setTabAt(tab, i, node);                        }                    }                }                if (binCount != 0)                    break;            }            else if ((fh = f.hash) == MOVED)                tab = helpTransfer(tab, f);            else {                boolean added = false;                synchronized (f) {                    if (tabAt(tab, i) == f) {                        if (fh >= 0) {                            binCount = 1;                            for (Node<K,V> e = f;; ++binCount) {                                K ek; V ev;                                if (e.hash == h &&                                    ((ek = e.key) == key ||                                     (ek != null && key.equals(ek)))) {                                    val = e.val;                                    break;                                }                                Node<K,V> pred = e;                                if ((e = e.next) == null) {                                    if ((val = mappingFunction.apply(key)) != null) {                                        added = true;                                        pred.next = new Node<K,V>(h, key, val, null);                                    }                                    break;                                }                            }                        }                        else if (f instanceof TreeBin) {                            binCount = 2;                            TreeBin<K,V> t = (TreeBin<K,V>)f;                            TreeNode<K,V> r, p;                            if ((r = t.root) != null &&                                (p = r.findTreeNode(h, key, null)) != null)                                val = p.val;                            else if ((val = mappingFunction.apply(key)) != null) {                                added = true;                                t.putTreeVal(h, key, val);                            }                        }                    }                }                if (binCount != 0) {                    if (binCount >= TREEIFY_THRESHOLD)                        treeifyBin(tab, i);                    if (!added)                        return val;                    break;                }            }        }        if (val != null)            addCount(1L, binCount);        return val;    }
    /**     * If the value for the specified key is present, attempts to     * compute a new mapping given the key and its current mapped     * value.  The entire method invocation is performed atomically.     * Some attempted update operations on this map by other threads     * may be blocked while computation is in progress, so the     * computation should be short and simple, and must not attempt to     * update any other mappings of this map.     *     * @param key key with which a value may be associated     * @param remappingFunction the function to compute a value     * @return the new value associated with the specified key, or null if none     * @throws NullPointerException if the specified key or remappingFunction     *         is null     * @throws IllegalStateException if the computation detectably     *         attempts a recursive update to this map that would     *         otherwise never complete     * @throws RuntimeException or Error if the remappingFunction does so,     *         in which case the mapping is unchanged     */    public V computeIfPresent(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {        if (key == null || remappingFunction == null)            throw new NullPointerException();        int h = spread(key.hashCode());        V val = null;        int delta = 0;        int binCount = 0;        for (Node<K,V>[] tab = table;;) {            Node<K,V> f; int n, i, fh;            if (tab == null || (n = tab.length) == 0)                tab = initTable();            else if ((f = tabAt(tab, i = (n - 1) & h)) == null)                break;            else if ((fh = f.hash) == MOVED)                tab = helpTransfer(tab, f);            else {                synchronized (f) {                    if (tabAt(tab, i) == f) {                        if (fh >= 0) {                            binCount = 1;                            for (Node<K,V> e = f, pred = null;; ++binCount) {                                K ek;                                if (e.hash == h &&                                    ((ek = e.key) == key ||                                     (ek != null && key.equals(ek)))) {                                    val = remappingFunction.apply(key, e.val);                                    if (val != null)                                        e.val = val;                                    else {                                        delta = -1;                                        Node<K,V> en = e.next;                                        if (pred != null)                                            pred.next = en;                                        else                                            setTabAt(tab, i, en);                                    }                                    break;                                }                                pred = e;                                if ((e = e.next) == null)                                    break;                            }                        }                        else if (f instanceof TreeBin) {                            binCount = 2;                            TreeBin<K,V> t = (TreeBin<K,V>)f;                            TreeNode<K,V> r, p;                            if ((r = t.root) != null &&                                (p = r.findTreeNode(h, key, null)) != null) {                                val = remappingFunction.apply(key, p.val);                                if (val != null)                                    p.val = val;                                else {                                    delta = -1;                                    if (t.removeTreeNode(p))                                        setTabAt(tab, i, untreeify(t.first));                                }                            }                        }                    }                }                if (binCount != 0)                    break;            }        }        if (delta != 0)            addCount((long)delta, binCount);        return val;    }
    /**     * Attempts to compute a mapping for the specified key and its     * current mapped value (or {@code null} if there is no current     * mapping). The entire method invocation is performed atomically.     * Some attempted update operations on this map by other threads     * may be blocked while computation is in progress, so the     * computation should be short and simple, and must not attempt to     * update any other mappings of this Map.     *     * @param key key with which the specified value is to be associated     * @param remappingFunction the function to compute a value     * @return the new value associated with the specified key, or null if none     * @throws NullPointerException if the specified key or remappingFunction     *         is null     * @throws IllegalStateException if the computation detectably     *         attempts a recursive update to this map that would     *         otherwise never complete     * @throws RuntimeException or Error if the remappingFunction does so,     *         in which case the mapping is unchanged     */    public V compute(K key,                     BiFunction<? super K, ? super V, ? extends V> remappingFunction) {        if (key == null || remappingFunction == null)            throw new NullPointerException();        int h = spread(key.hashCode());        V val = null;        int delta = 0;        int binCount = 0;        for (Node<K,V>[] tab = table;;) {            Node<K,V> f; int n, i, fh;            if (tab == null || (n = tab.length) == 0)                tab = initTable();            else if ((f = tabAt(tab, i = (n - 1) & h)) == null) {                Node<K,V> r = new ReservationNode<K,V>();                synchronized (r) {                    if (casTabAt(tab, i, null, r)) {                        binCount = 1;                        Node<K,V> node = null;                        try {                            if ((val = remappingFunction.apply(key, null)) != null) {                                delta = 1;                                node = new Node<K,V>(h, key, val, null);                            }                        } finally {                            setTabAt(tab, i, node);                        }                    }                }                if (binCount != 0)                    break;            }            else if ((fh = f.hash) == MOVED)                tab = helpTransfer(tab, f);            else {                synchronized (f) {                    if (tabAt(tab, i) == f) {                        if (fh >= 0) {                            binCount = 1;                            for (Node<K,V> e = f, pred = null;; ++binCount) {                                K ek;                                if (e.hash == h &&                                    ((ek = e.key) == key ||                                     (ek != null && key.equals(ek)))) {                                    val = remappingFunction.apply(key, e.val);                                    if (val != null)                                        e.val = val;                                    else {                                        delta = -1;                                        Node<K,V> en = e.next;                                        if (pred != null)                                            pred.next = en;                                        else                                            setTabAt(tab, i, en);                                    }                                    break;                                }                                pred = e;                                if ((e = e.next) == null) {                                    val = remappingFunction.apply(key, null);                                    if (val != null) {                                        delta = 1;                                        pred.next =                                            new Node<K,V>(h, key, val, null);                                    }                                    break;                                }                            }                        }                        else if (f instanceof TreeBin) {                            binCount = 1;                            TreeBin<K,V> t = (TreeBin<K,V>)f;                            TreeNode<K,V> r, p;                            if ((r = t.root) != null)                                p = r.findTreeNode(h, key, null);                            else                                p = null;                            V pv = (p == null) ? null : p.val;                            val = remappingFunction.apply(key, pv);                            if (val != null) {                                if (p != null)                                    p.val = val;                                else {                                    delta = 1;                                    t.putTreeVal(h, key, val);                                }                            }                            else if (p != null) {                                delta = -1;                                if (t.removeTreeNode(p))                                    setTabAt(tab, i, untreeify(t.first));                            }                        }                    }                }                if (binCount != 0) {                    if (binCount >= TREEIFY_THRESHOLD)                        treeifyBin(tab, i);                    break;                }            }        }        if (delta != 0)            addCount((long)delta, binCount);        return val;    }
    /**     * If the specified key is not already associated with a     * (non-null) value, associates it with the given value.     * Otherwise, replaces the value with the results of the given     * remapping function, or removes if {@code null}. The entire     * method invocation is performed atomically.  Some attempted     * update operations on this map by other threads may be blocked     * while computation is in progress, so the computation should be     * short and simple, and must not attempt to update any other     * mappings of this Map.     *     * @param key key with which the specified value is to be associated     * @param value the value to use if absent     * @param remappingFunction the function to recompute a value if present     * @return the new value associated with the specified key, or null if none     * @throws NullPointerException if the specified key or the     *         remappingFunction is null     * @throws RuntimeException or Error if the remappingFunction does so,     *         in which case the mapping is unchanged     */    public V merge(K key, V value, BiFunction<? super V, ? super V, ? extends V> remappingFunction) {        if (key == null || value == null || remappingFunction == null)            throw new NullPointerException();        int h = spread(key.hashCode());        V val = null;        int delta = 0;        int binCount = 0;        for (Node<K,V>[] tab = table;;) {            Node<K,V> f; int n, i, fh;            if (tab == null || (n = tab.length) == 0)                tab = initTable();            else if ((f = tabAt(tab, i = (n - 1) & h)) == null) {                if (casTabAt(tab, i, null, new Node<K,V>(h, key, value, null))) {                    delta = 1;                    val = value;                    break;                }            }            else if ((fh = f.hash) == MOVED)                tab = helpTransfer(tab, f);            else {                synchronized (f) {                    if (tabAt(tab, i) == f) {                        if (fh >= 0) {                            binCount = 1;                            for (Node<K,V> e = f, pred = null;; ++binCount) {                                K ek;                                if (e.hash == h &&                                    ((ek = e.key) == key ||                                     (ek != null && key.equals(ek)))) {                                    val = remappingFunction.apply(e.val, value);                                    if (val != null)                                        e.val = val;                                    else {                                        delta = -1;                                        Node<K,V> en = e.next;                                        if (pred != null)                                            pred.next = en;                                        else                                            setTabAt(tab, i, en);                                    }                                    break;                                }                                pred = e;                                if ((e = e.next) == null) {                                    delta = 1;                                    val = value;                                    pred.next =                                        new Node<K,V>(h, key, val, null);                                    break;                                }                            }                        }                        else if (f instanceof TreeBin) {                            binCount = 2;                            TreeBin<K,V> t = (TreeBin<K,V>)f;                            TreeNode<K,V> r = t.root;                            TreeNode<K,V> p = (r == null) ? null :                                r.findTreeNode(h, key, null);                            val = (p == null) ? value :                                remappingFunction.apply(p.val, value);                            if (val != null) {                                if (p != null)                                    p.val = val;                                else {                                    delta = 1;                                    t.putTreeVal(h, key, val);                                }                            }                            else if (p != null) {                                delta = -1;                                if (t.removeTreeNode(p))                                    setTabAt(tab, i, untreeify(t.first));                            }                        }                    }                }                if (binCount != 0) {                    if (binCount >= TREEIFY_THRESHOLD)                        treeifyBin(tab, i);                    break;                }            }        }        if (delta != 0)            addCount((long)delta, binCount);        return val;    }
    // Hashtable legacy methods
    /**     * Legacy method testing if some key maps into the specified value     * in this table.  This method is identical in functionality to     * {@link #containsValue(Object)}, and exists solely to ensure     * full compatibility with class {@link java.util.Hashtable},     * which supported this method prior to introduction of the     * Java Collections framework.     *     * @param  value a value to search for     * @return {@code true} if and only if some key maps to the     *         {@code value} argument in this table as     *         determined by the {@code equals} method;     *         {@code false} otherwise     * @throws NullPointerException if the specified value is null     */    public boolean contains(Object value) {        return containsValue(value);    }
    /**     * Returns an enumeration of the keys in this table.     *     * @return an enumeration of the keys in this table     * @see #keySet()     */    public Enumeration<K> keys() {        Node<K,V>[] t;        int f = (t = table) == null ? 0 : t.length;        return new KeyIterator<K,V>(t, f, 0, f, this);    }
    /**     * Returns an enumeration of the values in this table.     *     * @return an enumeration of the values in this table     * @see #values()     */    public Enumeration<V> elements() {        Node<K,V>[] t;        int f = (t = table) == null ? 0 : t.length;        return new ValueIterator<K,V>(t, f, 0, f, this);    }
    // ConcurrentHashMap-only methods
    /**     * Returns the number of mappings. This method should be used     * instead of {@link #size} because a ConcurrentHashMap may     * contain more mappings than can be represented as an int. The     * value returned is an estimate; the actual count may differ if     * there are concurrent insertions or removals.     *     * @return the number of mappings     * @since 1.8     */    public long mappingCount() {        long n = sumCount();        return (n < 0L) ? 0L : n; // ignore transient negative values    }
    /**     * Creates a new {@link Set} backed by a ConcurrentHashMap     * from the given type to {@code Boolean.TRUE}.     *     * @param <K> the element type of the returned set     * @return the new set     * @since 1.8     */    public static <K> KeySetView<K,Boolean> newKeySet() {        return new KeySetView<K,Boolean>            (new ConcurrentHashMap<K,Boolean>(), Boolean.TRUE);    }
    /**     * Creates a new {@link Set} backed by a ConcurrentHashMap     * from the given type to {@code Boolean.TRUE}.     *     * @param initialCapacity The implementation performs internal     * sizing to accommodate this many elements.     * @param <K> the element type of the returned set     * @return the new set     * @throws IllegalArgumentException if the initial capacity of     * elements is negative     * @since 1.8     */    public static <K> KeySetView<K,Boolean> newKeySet(int initialCapacity) {        return new KeySetView<K,Boolean>            (new ConcurrentHashMap<K,Boolean>(initialCapacity), Boolean.TRUE);    }
    /**     * Returns a {@link Set} view of the keys in this map, using the     * given common mapped value for any additions (i.e., {@link     * Collection#add} and {@link Collection#addAll(Collection)}).     * This is of course only appropriate if it is acceptable to use     * the same value for all additions from this view.     *     * @param mappedValue the mapped value to use for any additions     * @return the set view     * @throws NullPointerException if the mappedValue is null     */    public KeySetView<K,V> keySet(V mappedValue) {        if (mappedValue == null)            throw new NullPointerException();        return new KeySetView<K,V>(this, mappedValue);    }
    /* ---------------- Special Nodes -------------- */
    /**     * A node inserted at head of bins during transfer operations.     */    static final class ForwardingNode<K,V> extends Node<K,V> {        final Node<K,V>[] nextTable;        ForwardingNode(Node<K,V>[] tab) {            super(MOVED, null, null, null);            this.nextTable = tab;        }
        Node<K,V> find(int h, Object k) {            // loop to avoid arbitrarily deep recursion on forwarding nodes            outer: for (Node<K,V>[] tab = nextTable;;) {                Node<K,V> e; int n;                if (k == null || tab == null || (n = tab.length) == 0 ||                    (e = tabAt(tab, (n - 1) & h)) == null)                    return null;                for (;;) {                    int eh; K ek;                    if ((eh = e.hash) == h &&                        ((ek = e.key) == k || (ek != null && k.equals(ek))))                        return e;                    if (eh < 0) {                        if (e instanceof ForwardingNode) {                            tab = ((ForwardingNode<K,V>)e).nextTable;                            continue outer;                        }                        else                            return e.find(h, k);                    }                    if ((e = e.next) == null)                        return null;                }            }        }    }
    /**     * A place-holder node used in computeIfAbsent and compute     */    static final class ReservationNode<K,V> extends Node<K,V> {        ReservationNode() {            super(RESERVED, null, null, null);        }
        Node<K,V> find(int h, Object k) {            return null;        }    }
    /* ---------------- Table Initialization and Resizing -------------- */
    /**     * Returns the stamp bits for resizing a table of size n.     * Must be negative when shifted left by RESIZE_STAMP_SHIFT.     */    static final int resizeStamp(int n) {        return Integer.numberOfLeadingZeros(n) | (1 << (RESIZE_STAMP_BITS - 1));    }
    /**     * Initializes table, using the size recorded in sizeCtl.     */    private final Node<K,V>[] initTable() {        Node<K,V>[] tab; int sc;        while ((tab = table) == null || tab.length == 0) {            if ((sc = sizeCtl) < 0)                Thread.yield(); // lost initialization race; just spin            else if (U.compareAndSwapInt(this, SIZECTL, sc, -1)) {                try {                    if ((tab = table) == null || tab.length == 0) {                        int n = (sc > 0) ? sc : DEFAULT_CAPACITY;                        @SuppressWarnings("unchecked")                        Node<K,V>[] nt = (Node<K,V>[])new Node<?,?>[n];                        table = tab = nt;                        sc = n - (n >>> 2);                    }                } finally {                    sizeCtl = sc;                }                break;            }        }        return tab;    }
    /**     * Adds to count, and if table is too small and not already     * resizing, initiates transfer. If already resizing, helps     * perform transfer if work is available.  Rechecks occupancy     * after a transfer to see if another resize is already needed     * because resizings are lagging additions.     *     * @param x the count to add     * @param check if <0, don't check resize, if <= 1 only check if uncontended     */    private final void addCount(long x, int check) {        CounterCell[] as; long b, s;        if ((as = counterCells) != null ||            !U.compareAndSwapLong(this, BASECOUNT, b = baseCount, s = b + x)) {            CounterCell a; long v; int m;            boolean uncontended = true;            if (as == null || (m = as.length - 1) < 0 ||                (a = as[ThreadLocalRandom.getProbe() & m]) == null ||                !(uncontended =                  U.compareAndSwapLong(a, CELLVALUE, v = a.value, v + x))) {                fullAddCount(x, uncontended);                return;            }            if (check <= 1)                return;            s = sumCount();        }        if (check >= 0) {            Node<K,V>[] tab, nt; int n, sc;            while (s >= (long)(sc = sizeCtl) && (tab = table) != null &&                   (n = tab.length) < MAXIMUM_CAPACITY) {                int rs = resizeStamp(n);                if (sc < 0) {                    if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 ||                        sc == rs + MAX_RESIZERS || (nt = nextTable) == null ||                        transferIndex <= 0)                        break;                    if (U.compareAndSwapInt(this, SIZECTL, sc, sc + 1))                        transfer(tab, nt);                }                else if (U.compareAndSwapInt(this, SIZECTL, sc,                                             (rs << RESIZE_STAMP_SHIFT) + 2))                    transfer(tab, null);                s = sumCount();            }        }    }
    /**     * Helps transfer if a resize is in progress.     */    final Node<K,V>[] helpTransfer(Node<K,V>[] tab, Node<K,V> f) {        Node<K,V>[] nextTab; int sc;        if (tab != null && (f instanceof ForwardingNode) &&            (nextTab = ((ForwardingNode<K,V>)f).nextTable) != null) {            int rs = resizeStamp(tab.length);            while (nextTab == nextTable && table == tab &&                   (sc = sizeCtl) < 0) {                if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 ||                    sc == rs + MAX_RESIZERS || transferIndex <= 0)                    break;                if (U.compareAndSwapInt(this, SIZECTL, sc, sc + 1)) {                    transfer(tab, nextTab);                    break;                }            }            return nextTab;        }        return table;    }
    /**     * Tries to presize table to accommodate the given number of elements.     *     * @param size number of elements (doesn't need to be perfectly accurate)     */    private final void tryPresize(int size) {        int c = (size >= (MAXIMUM_CAPACITY >>> 1)) ? MAXIMUM_CAPACITY :            tableSizeFor(size + (size >>> 1) + 1);        int sc;        while ((sc = sizeCtl) >= 0) {            Node<K,V>[] tab = table; int n;            if (tab == null || (n = tab.length) == 0) {                n = (sc > c) ? sc : c;                if (U.compareAndSwapInt(this, SIZECTL, sc, -1)) {                    try {                        if (table == tab) {                            @SuppressWarnings("unchecked")                            Node<K,V>[] nt = (Node<K,V>[])new Node<?,?>[n];                            table = nt;                            sc = n - (n >>> 2);                        }                    } finally {                        sizeCtl = sc;                    }                }            }            else if (c <= sc || n >= MAXIMUM_CAPACITY)                break;            else if (tab == table) {                int rs = resizeStamp(n);                if (sc < 0) {                    Node<K,V>[] nt;                    if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 ||                        sc == rs + MAX_RESIZERS || (nt = nextTable) == null ||                        transferIndex <= 0)                        break;                    if (U.compareAndSwapInt(this, SIZECTL, sc, sc + 1))                        transfer(tab, nt);                }                else if (U.compareAndSwapInt(this, SIZECTL, sc,                                             (rs << RESIZE_STAMP_SHIFT) + 2))                    transfer(tab, null);            }        }    }
    /**     * Moves and/or copies the nodes in each bin to new table. See     * above for explanation.     */    private final void transfer(Node<K,V>[] tab, Node<K,V>[] nextTab) {        int n = tab.length, stride;        if ((stride = (NCPU > 1) ? (n >>> 3) / NCPU : n) < MIN_TRANSFER_STRIDE)            stride = MIN_TRANSFER_STRIDE; // subdivide range        if (nextTab == null) {            // initiating            try {                @SuppressWarnings("unchecked")                Node<K,V>[] nt = (Node<K,V>[])new Node<?,?>[n << 1];                nextTab = nt;            } catch (Throwable ex) {      // try to cope with OOME                sizeCtl = Integer.MAX_VALUE;                return;            }            nextTable = nextTab;            transferIndex = n;        }        int nextn = nextTab.length;        ForwardingNode<K,V> fwd = new ForwardingNode<K,V>(nextTab);        boolean advance = true;        boolean finishing = false; // to ensure sweep before committing nextTab        for (int i = 0, bound = 0;;) {            Node<K,V> f; int fh;            while (advance) {                int nextIndex, nextBound;                if (--i >= bound || finishing)                    advance = false;                else if ((nextIndex = transferIndex) <= 0) {                    i = -1;                    advance = false;                }                else if (U.compareAndSwapInt                         (this, TRANSFERINDEX, nextIndex,                          nextBound = (nextIndex > stride ?                                       nextIndex - stride : 0))) {                    bound = nextBound;                    i = nextIndex - 1;                    advance = false;                }            }            if (i < 0 || i >= n || i + n >= nextn) {                int sc;                if (finishing) {                    nextTable = null;                    table = nextTab;                    sizeCtl = (n << 1) - (n >>> 1);                    return;                }                if (U.compareAndSwapInt(this, SIZECTL, sc = sizeCtl, sc - 1)) {                    if ((sc - 2) != resizeStamp(n) << RESIZE_STAMP_SHIFT)                        return;                    finishing = advance = true;                    i = n; // recheck before commit                }            }            else if ((f = tabAt(tab, i)) == null)                advance = casTabAt(tab, i, null, fwd);            else if ((fh = f.hash) == MOVED)                advance = true; // already processed            else {                synchronized (f) {                    if (tabAt(tab, i) == f) {                        Node<K,V> ln, hn;                        if (fh >= 0) {                            int runBit = fh & n;                            Node<K,V> lastRun = f;                            for (Node<K,V> p = f.next; p != null; p = p.next) {                                int b = p.hash & n;                                if (b != runBit) {                                    runBit = b;                                    lastRun = p;                                }                            }                            if (runBit == 0) {                                ln = lastRun;                                hn = null;                            }                            else {                                hn = lastRun;                                ln = null;                            }                            for (Node<K,V> p = f; p != lastRun; p = p.next) {                                int ph = p.hash; K pk = p.key; V pv = p.val;                                if ((ph & n) == 0)                                    ln = new Node<K,V>(ph, pk, pv, ln);                                else                                    hn = new Node<K,V>(ph, pk, pv, hn);                            }                            setTabAt(nextTab, i, ln);                            setTabAt(nextTab, i + n, hn);                            setTabAt(tab, i, fwd);                            advance = true;                        }                        else if (f instanceof TreeBin) {                            TreeBin<K,V> t = (TreeBin<K,V>)f;                            TreeNode<K,V> lo = null, loTail = null;                            TreeNode<K,V> hi = null, hiTail = null;                            int lc = 0, hc = 0;                            for (Node<K,V> e = t.first; e != null; e = e.next) {                                int h = e.hash;                                TreeNode<K,V> p = new TreeNode<K,V>                                    (h, e.key, e.val, null, null);                                if ((h & n) == 0) {                                    if ((p.prev = loTail) == null)                                        lo = p;                                    else                                        loTail.next = p;                                    loTail = p;                                    ++lc;                                }                                else {                                    if ((p.prev = hiTail) == null)                                        hi = p;                                    else                                        hiTail.next = p;                                    hiTail = p;                                    ++hc;                                }                            }                            ln = (lc <= UNTREEIFY_THRESHOLD) ? untreeify(lo) :                                (hc != 0) ? new TreeBin<K,V>(lo) : t;                            hn = (hc <= UNTREEIFY_THRESHOLD) ? untreeify(hi) :                                (lc != 0) ? new TreeBin<K,V>(hi) : t;                            setTabAt(nextTab, i, ln);                            setTabAt(nextTab, i + n, hn);                            setTabAt(tab, i, fwd);                            advance = true;                        }                    }                }            }        }    }
    /* ---------------- Counter support -------------- */
    /**     * A padded cell for distributing counts.  Adapted from LongAdder     * and Striped64.  See their internal docs for explanation.     */    @sun.misc.Contended static final class CounterCell {        volatile long value;        CounterCell(long x) { value = x; }    }
    final long sumCount() {        CounterCell[] as = counterCells; CounterCell a;        long sum = baseCount;        if (as != null) {            for (int i = 0; i < as.length; ++i) {                if ((a = as[i]) != null)                    sum += a.value;            }        }        return sum;    }
    // See LongAdder version for explanation    private final void fullAddCount(long x, boolean wasUncontended) {        int h;        if ((h = ThreadLocalRandom.getProbe()) == 0) {            ThreadLocalRandom.localInit();      // force initialization            h = ThreadLocalRandom.getProbe();            wasUncontended = true;        }        boolean collide = false;                // True if last slot nonempty        for (;;) {            CounterCell[] as; CounterCell a; int n; long v;            if ((as = counterCells) != null && (n = as.length) > 0) {                if ((a = as[(n - 1) & h]) == null) {                    if (cellsBusy == 0) {            // Try to attach new Cell                        CounterCell r = new CounterCell(x); // Optimistic create                        if (cellsBusy == 0 &&                            U.compareAndSwapInt(this, CELLSBUSY, 0, 1)) {                            boolean created = false;                            try {               // Recheck under lock                                CounterCell[] rs; int m, j;                                if ((rs = counterCells) != null &&                                    (m = rs.length) > 0 &&                                    rs[j = (m - 1) & h] == null) {                                    rs[j] = r;                                    created = true;                                }                            } finally {                                cellsBusy = 0;                            }                            if (created)                                break;                            continue;           // Slot is now non-empty                        }                    }                    collide = false;                }                else if (!wasUncontended)       // CAS already known to fail                    wasUncontended = true;      // Continue after rehash                else if (U.compareAndSwapLong(a, CELLVALUE, v = a.value, v + x))                    break;                else if (counterCells != as || n >= NCPU)                    collide = false;            // At max size or stale                else if (!collide)                    collide = true;                else if (cellsBusy == 0 &&                         U.compareAndSwapInt(this, CELLSBUSY, 0, 1)) {                    try {                        if (counterCells == as) {// Expand table unless stale                            CounterCell[] rs = new CounterCell[n << 1];                            for (int i = 0; i < n; ++i)                                rs[i] = as[i];                            counterCells = rs;                        }                    } finally {                        cellsBusy = 0;                    }                    collide = false;                    continue;                   // Retry with expanded table                }                h = ThreadLocalRandom.advanceProbe(h);            }            else if (cellsBusy == 0 && counterCells == as &&                     U.compareAndSwapInt(this, CELLSBUSY, 0, 1)) {                boolean init = false;                try {                           // Initialize table                    if (counterCells == as) {                        CounterCell[] rs = new CounterCell[2];                        rs[h & 1] = new CounterCell(x);                        counterCells = rs;                        init = true;                    }                } finally {                    cellsBusy = 0;                }                if (init)                    break;            }            else if (U.compareAndSwapLong(this, BASECOUNT, v = baseCount, v + x))                break;                          // Fall back on using base        }    }
    /* ---------------- Conversion from/to TreeBins -------------- */
    /**     * Replaces all linked nodes in bin at given index unless table is     * too small, in which case resizes instead.     */    private final void treeifyBin(Node<K,V>[] tab, int index) {        Node<K,V> b; int n, sc;        if (tab != null) {            if ((n = tab.length) < MIN_TREEIFY_CAPACITY)                tryPresize(n << 1);            else if ((b = tabAt(tab, index)) != null && b.hash >= 0) {                synchronized (b) {                    if (tabAt(tab, index) == b) {                        TreeNode<K,V> hd = null, tl = null;                        for (Node<K,V> e = b; e != null; e = e.next) {                            TreeNode<K,V> p =                                new TreeNode<K,V>(e.hash, e.key, e.val,                                                  null, null);                            if ((p.prev = tl) == null)                                hd = p;                            else                                tl.next = p;                            tl = p;                        }                        setTabAt(tab, index, new TreeBin<K,V>(hd));                    }                }            }        }    }
    /**     * Returns a list on non-TreeNodes replacing those in given list.     */    static <K,V> Node<K,V> untreeify(Node<K,V> b) {        Node<K,V> hd = null, tl = null;        for (Node<K,V> q = b; q != null; q = q.next) {            Node<K,V> p = new Node<K,V>(q.hash, q.key, q.val, null);            if (tl == null)                hd = p;            else                tl.next = p;            tl = p;        }        return hd;    }
    /* ---------------- TreeNodes -------------- */
    /**     * Nodes for use in TreeBins     */    static final class TreeNode<K,V> extends Node<K,V> {        TreeNode<K,V> parent;  // red-black tree links        TreeNode<K,V> left;        TreeNode<K,V> right;        TreeNode<K,V> prev;    // needed to unlink next upon deletion        boolean red;
        TreeNode(int hash, K key, V val, Node<K,V> next,                 TreeNode<K,V> parent) {            super(hash, key, val, next);            this.parent = parent;        }
        Node<K,V> find(int h, Object k) {            return findTreeNode(h, k, null);        }
        /**         * Returns the TreeNode (or null if not found) for the given key         * starting at given root.         */        final TreeNode<K,V> findTreeNode(int h, Object k, Class<?> kc) {            if (k != null) {                TreeNode<K,V> p = this;                do  {                    int ph, dir; K pk; TreeNode<K,V> q;                    TreeNode<K,V> pl = p.left, pr = p.right;                    if ((ph = p.hash) > h)                        p = pl;                    else if (ph < h)                        p = pr;                    else if ((pk = p.key) == k || (pk != null && k.equals(pk)))                        return p;                    else if (pl == null)                        p = pr;                    else if (pr == null)                        p = pl;                    else if ((kc != null ||                              (kc = comparableClassFor(k)) != null) &&                             (dir = compareComparables(kc, k, pk)) != 0)                        p = (dir < 0) ? pl : pr;                    else if ((q = pr.findTreeNode(h, k, kc)) != null)                        return q;                    else                        p = pl;                } while (p != null);            }            return null;        }    }
    /* ---------------- TreeBins -------------- */
    /**     * TreeNodes used at the heads of bins. TreeBins do not hold user     * keys or values, but instead point to list of TreeNodes and     * their root. They also maintain a parasitic read-write lock     * forcing writers (who hold bin lock) to wait for readers (who do     * not) to complete before tree restructuring operations.     */    static final class TreeBin<K,V> extends Node<K,V> {        TreeNode<K,V> root;        volatile TreeNode<K,V> first;        volatile Thread waiter;        volatile int lockState;        // values for lockState        static final int WRITER = 1; // set while holding write lock        static final int WAITER = 2; // set when waiting for write lock        static final int READER = 4; // increment value for setting read lock
        /**         * Tie-breaking utility for ordering insertions when equal         * hashCodes and non-comparable. We don't require a total         * order, just a consistent insertion rule to maintain         * equivalence across rebalancings. Tie-breaking further than         * necessary simplifies testing a bit.         */        static int tieBreakOrder(Object a, Object b) {            int d;            if (a == null || b == null ||                (d = a.getClass().getName().                 compareTo(b.getClass().getName())) == 0)                d = (System.identityHashCode(a) <= System.identityHashCode(b) ?                     -1 : 1);            return d;        }
        /**         * Creates bin with initial set of nodes headed by b.         */        TreeBin(TreeNode<K,V> b) {            super(TREEBIN, null, null, null);            this.first = b;            TreeNode<K,V> r = null;            for (TreeNode<K,V> x = b, next; x != null; x = next) {                next = (TreeNode<K,V>)x.next;                x.left = x.right = null;                if (r == null) {                    x.parent = null;                    x.red = false;                    r = x;                }                else {                    K k = x.key;                    int h = x.hash;                    Class<?> kc = null;                    for (TreeNode<K,V> p = r;;) {                        int dir, ph;                        K pk = p.key;                        if ((ph = p.hash) > h)                            dir = -1;                        else if (ph < h)                            dir = 1;                        else if ((kc == null &&                                  (kc = comparableClassFor(k)) == null) ||                                 (dir = compareComparables(kc, k, pk)) == 0)                            dir = tieBreakOrder(k, pk);                            TreeNode<K,V> xp = p;                        if ((p = (dir <= 0) ? p.left : p.right) == null) {                            x.parent = xp;                            if (dir <= 0)                                xp.left = x;                            else                                xp.right = x;                            r = balanceInsertion(r, x);                            break;                        }                    }                }            }            this.root = r;            assert checkInvariants(root);        }
        /**         * Acquires write lock for tree restructuring.         */        private final void lockRoot() {            if (!U.compareAndSwapInt(this, LOCKSTATE, 0, WRITER))                contendedLock(); // offload to separate method        }
        /**         * Releases write lock for tree restructuring.         */        private final void unlockRoot() {            lockState = 0;        }
        /**         * Possibly blocks awaiting root lock.         */        private final void contendedLock() {            boolean waiting = false;            for (int s;;) {                if (((s = lockState) & ~WAITER) == 0) {                    if (U.compareAndSwapInt(this, LOCKSTATE, s, WRITER)) {                        if (waiting)                            waiter = null;                        return;                    }                }                else if ((s & WAITER) == 0) {                    if (U.compareAndSwapInt(this, LOCKSTATE, s, s | WAITER)) {                        waiting = true;                        waiter = Thread.currentThread();                    }                }                else if (waiting)                    LockSupport.park(this);            }        }
        /**         * Returns matching node or null if none. Tries to search         * using tree comparisons from root, but continues linear         * search when lock not available.         */        final Node<K,V> find(int h, Object k) {            if (k != null) {                for (Node<K,V> e = first; e != null; ) {                    int s; K ek;                    if (((s = lockState) & (WAITER|WRITER)) != 0) {                        if (e.hash == h &&                            ((ek = e.key) == k || (ek != null && k.equals(ek))))                            return e;                        e = e.next;                    }                    else if (U.compareAndSwapInt(this, LOCKSTATE, s,                                                 s + READER)) {                        TreeNode<K,V> r, p;                        try {                            p = ((r = root) == null ? null :                                 r.findTreeNode(h, k, null));                        } finally {                            Thread w;                            if (U.getAndAddInt(this, LOCKSTATE, -READER) ==                                (READER|WAITER) && (w = waiter) != null)                                LockSupport.unpark(w);                        }                        return p;                    }                }            }            return null;        }
        /**         * Finds or adds a node.         * @return null if added         */        final TreeNode<K,V> putTreeVal(int h, K k, V v) {            Class<?> kc = null;            boolean searched = false;            for (TreeNode<K,V> p = root;;) {                int dir, ph; K pk;                if (p == null) {                    first = root = new TreeNode<K,V>(h, k, v, null, null);                    break;                }                else if ((ph = p.hash) > h)                    dir = -1;                else if (ph < h)                    dir = 1;                else if ((pk = p.key) == k || (pk != null && k.equals(pk)))                    return p;                else if ((kc == null &&                          (kc = comparableClassFor(k)) == null) ||                         (dir = compareComparables(kc, k, pk)) == 0) {                    if (!searched) {                        TreeNode<K,V> q, ch;                        searched = true;                        if (((ch = p.left) != null &&                             (q = ch.findTreeNode(h, k, kc)) != null) ||                            ((ch = p.right) != null &&                             (q = ch.findTreeNode(h, k, kc)) != null))                            return q;                    }                    dir = tieBreakOrder(k, pk);                }
                TreeNode<K,V> xp = p;                if ((p = (dir <= 0) ? p.left : p.right) == null) {                    TreeNode<K,V> x, f = first;                    first = x = new TreeNode<K,V>(h, k, v, f, xp);                    if (f != null)                        f.prev = x;                    if (dir <= 0)                        xp.left = x;                    else                        xp.right = x;                    if (!xp.red)                        x.red = true;                    else {                        lockRoot();                        try {                            root = balanceInsertion(root, x);                        } finally {                            unlockRoot();                        }                    }                    break;                }            }            assert checkInvariants(root);            return null;        }
        /**         * Removes the given node, that must be present before this         * call.  This is messier than typical red-black deletion code         * because we cannot swap the contents of an interior node         * with a leaf successor that is pinned by "next" pointers         * that are accessible independently of lock. So instead we         * swap the tree linkages.         *         * @return true if now too small, so should be untreeified         */        final boolean removeTreeNode(TreeNode<K,V> p) {            TreeNode<K,V> next = (TreeNode<K,V>)p.next;            TreeNode<K,V> pred = p.prev;  // unlink traversal pointers            TreeNode<K,V> r, rl;            if (pred == null)                first = next;            else                pred.next = next;            if (next != null)                next.prev = pred;            if (first == null) {                root = null;                return true;            }            if ((r = root) == null || r.right == null || // too small                (rl = r.left) == null || rl.left == null)                return true;            lockRoot();            try {                TreeNode<K,V> replacement;                TreeNode<K,V> pl = p.left;                TreeNode<K,V> pr = p.right;                if (pl != null && pr != null) {                    TreeNode<K,V> s = pr, sl;                    while ((sl = s.left) != null) // find successor                        s = sl;                    boolean c = s.red; s.red = p.red; p.red = c; // swap colors                    TreeNode<K,V> sr = s.right;                    TreeNode<K,V> pp = p.parent;                    if (s == pr) { // p was s's direct parent                        p.parent = s;                        s.right = p;                    }                    else {                        TreeNode<K,V> sp = s.parent;                        if ((p.parent = sp) != null) {                            if (s == sp.left)                                sp.left = p;                            else                                sp.right = p;                        }                        if ((s.right = pr) != null)                            pr.parent = s;                    }                    p.left = null;                    if ((p.right = sr) != null)                        sr.parent = p;                    if ((s.left = pl) != null)                        pl.parent = s;                    if ((s.parent = pp) == null)                        r = s;                    else if (p == pp.left)                        pp.left = s;                    else                        pp.right = s;                    if (sr != null)                        replacement = sr;                    else                        replacement = p;                }                else if (pl != null)                    replacement = pl;                else if (pr != null)                    replacement = pr;                else                    replacement = p;                if (replacement != p) {                    TreeNode<K,V> pp = replacement.parent = p.parent;                    if (pp == null)                        r = replacement;                    else if (p == pp.left)                        pp.left = replacement;                    else                        pp.right = replacement;                    p.left = p.right = p.parent = null;                }
                root = (p.red) ? r : balanceDeletion(r, replacement);
                if (p == replacement) {  // detach pointers                    TreeNode<K,V> pp;                    if ((pp = p.parent) != null) {                        if (p == pp.left)                            pp.left = null;                        else if (p == pp.right)                            pp.right = null;                        p.parent = null;                    }                }            } finally {                unlockRoot();            }            assert checkInvariants(root);            return false;        }
        /* ------------------------------------------------------------ */        // Red-black tree methods, all adapted from CLR
        static <K,V> TreeNode<K,V> rotateLeft(TreeNode<K,V> root,                                              TreeNode<K,V> p) {            TreeNode<K,V> r, pp, rl;            if (p != null && (r = p.right) != null) {                if ((rl = p.right = r.left) != null)                    rl.parent = p;                if ((pp = r.parent = p.parent) == null)                    (root = r).red = false;                else if (pp.left == p)                    pp.left = r;                else                    pp.right = r;                r.left = p;                p.parent = r;            }            return root;        }
        static <K,V> TreeNode<K,V> rotateRight(TreeNode<K,V> root,                                               TreeNode<K,V> p) {            TreeNode<K,V> l, pp, lr;            if (p != null && (l = p.left) != null) {                if ((lr = p.left = l.right) != null)                    lr.parent = p;                if ((pp = l.parent = p.parent) == null)                    (root = l).red = false;                else if (pp.right == p)                    pp.right = l;                else                    pp.left = l;                l.right = p;                p.parent = l;            }            return root;        }
        static <K,V> TreeNode<K,V> balanceInsertion(TreeNode<K,V> root,                                                    TreeNode<K,V> x) {            x.red = true;            for (TreeNode<K,V> xp, xpp, xppl, xppr;;) {                if ((xp = x.parent) == null) {                    x.red = false;                    return x;                }                else if (!xp.red || (xpp = xp.parent) == null)                    return root;                if (xp == (xppl = xpp.left)) {                    if ((xppr = xpp.right) != null && xppr.red) {                        xppr.red = false;                        xp.red = false;                        xpp.red = true;                        x = xpp;                    }                    else {                        if (x == xp.right) {                            root = rotateLeft(root, x = xp);                            xpp = (xp = x.parent) == null ? null : xp.parent;                        }                        if (xp != null) {                            xp.red = false;                            if (xpp != null) {                                xpp.red = true;                                root = rotateRight(root, xpp);                            }                        }                    }                }                else {                    if (xppl != null && xppl.red) {                        xppl.red = false;                        xp.red = false;                        xpp.red = true;                        x = xpp;                    }                    else {                        if (x == xp.left) {                            root = rotateRight(root, x = xp);                            xpp = (xp = x.parent) == null ? null : xp.parent;                        }                        if (xp != null) {                            xp.red = false;                            if (xpp != null) {                                xpp.red = true;                                root = rotateLeft(root, xpp);                            }                        }                    }                }            }        }
        static <K,V> TreeNode<K,V> balanceDeletion(TreeNode<K,V> root,                                                   TreeNode<K,V> x) {            for (TreeNode<K,V> xp, xpl, xpr;;)  {                if (x == null || x == root)                    return root;                else if ((xp = x.parent) == null) {                    x.red = false;                    return x;                }                else if (x.red) {                    x.red = false;                    return root;                }                else if ((xpl = xp.left) == x) {                    if ((xpr = xp.right) != null && xpr.red) {                        xpr.red = false;                        xp.red = true;                        root = rotateLeft(root, xp);                        xpr = (xp = x.parent) == null ? null : xp.right;                    }                    if (xpr == null)                        x = xp;                    else {                        TreeNode<K,V> sl = xpr.left, sr = xpr.right;                        if ((sr == null || !sr.red) &&                            (sl == null || !sl.red)) {                            xpr.red = true;                            x = xp;                        }                        else {                            if (sr == null || !sr.red) {                                if (sl != null)                                    sl.red = false;                                xpr.red = true;                                root = rotateRight(root, xpr);                                xpr = (xp = x.parent) == null ?                                    null : xp.right;                            }                            if (xpr != null) {                                xpr.red = (xp == null) ? false : xp.red;                                if ((sr = xpr.right) != null)                                    sr.red = false;                            }                            if (xp != null) {                                xp.red = false;                                root = rotateLeft(root, xp);                            }                            x = root;                        }                    }                }                else { // symmetric                    if (xpl != null && xpl.red) {                        xpl.red = false;                        xp.red = true;                        root = rotateRight(root, xp);                        xpl = (xp = x.parent) == null ? null : xp.left;                    }                    if (xpl == null)                        x = xp;                    else {                        TreeNode<K,V> sl = xpl.left, sr = xpl.right;                        if ((sl == null || !sl.red) &&                            (sr == null || !sr.red)) {                            xpl.red = true;                            x = xp;                        }                        else {                            if (sl == null || !sl.red) {                                if (sr != null)                                    sr.red = false;                                xpl.red = true;                                root = rotateLeft(root, xpl);                                xpl = (xp = x.parent) == null ?                                    null : xp.left;                            }                            if (xpl != null) {                                xpl.red = (xp == null) ? false : xp.red;                                if ((sl = xpl.left) != null)                                    sl.red = false;                            }                            if (xp != null) {                                xp.red = false;                                root = rotateRight(root, xp);                            }                            x = root;                        }                    }                }            }        }
        /**         * Recursive invariant check         */        static <K,V> boolean checkInvariants(TreeNode<K,V> t) {            TreeNode<K,V> tp = t.parent, tl = t.left, tr = t.right,                tb = t.prev, tn = (TreeNode<K,V>)t.next;            if (tb != null && tb.next != t)                return false;            if (tn != null && tn.prev != t)                return false;            if (tp != null && t != tp.left && t != tp.right)                return false;            if (tl != null && (tl.parent != t || tl.hash > t.hash))                return false;            if (tr != null && (tr.parent != t || tr.hash < t.hash))                return false;            if (t.red && tl != null && tl.red && tr != null && tr.red)                return false;            if (tl != null && !checkInvariants(tl))                return false;            if (tr != null && !checkInvariants(tr))                return false;            return true;        }
        private static final sun.misc.Unsafe U;        private static final long LOCKSTATE;        static {            try {                U = sun.misc.Unsafe.getUnsafe();                Class<?> k = TreeBin.class;                LOCKSTATE = U.objectFieldOffset                    (k.getDeclaredField("lockState"));            } catch (Exception e) {                throw new Error(e);            }        }    }
    /* ----------------Table Traversal -------------- */
    /**     * Records the table, its length, and current traversal index for a     * traverser that must process a region of a forwarded table before     * proceeding with current table.     */    static final class TableStack<K,V> {        int length;        int index;        Node<K,V>[] tab;        TableStack<K,V> next;    }
    /**     * Encapsulates traversal for methods such as containsValue; also     * serves as a base class for other iterators and spliterators.     *     * Method advance visits once each still-valid node that was     * reachable upon iterator construction. It might miss some that     * were added to a bin after the bin was visited, which is OK wrt     * consistency guarantees. Maintaining this property in the face     * of possible ongoing resizes requires a fair amount of     * bookkeeping state that is difficult to optimize away amidst     * volatile accesses.  Even so, traversal maintains reasonable     * throughput.     *     * Normally, iteration proceeds bin-by-bin traversing lists.     * However, if the table has been resized, then all future steps     * must traverse both the bin at the current index as well as at     * (index + baseSize); and so on for further resizings. To     * paranoically cope with potential sharing by users of iterators     * across threads, iteration terminates if a bounds checks fails     * for a table read.     */    static class Traverser<K,V> {        Node<K,V>[] tab;        // current table; updated if resized        Node<K,V> next;         // the next entry to use        TableStack<K,V> stack, spare; // to save/restore on ForwardingNodes        int index;              // index of bin to use next        int baseIndex;          // current index of initial table        int baseLimit;          // index bound for initial table        final int baseSize;     // initial table size
        Traverser(Node<K,V>[] tab, int size, int index, int limit) {            this.tab = tab;            this.baseSize = size;            this.baseIndex = this.index = index;            this.baseLimit = limit;            this.next = null;        }
        /**         * Advances if possible, returning next valid node, or null if none.         */        final Node<K,V> advance() {            Node<K,V> e;            if ((e = next) != null)                e = e.next;            for (;;) {                Node<K,V>[] t; int i, n;  // must use locals in checks                if (e != null)                    return next = e;                if (baseIndex >= baseLimit || (t = tab) == null ||                    (n = t.length) <= (i = index) || i < 0)                    return next = null;                if ((e = tabAt(t, i)) != null && e.hash < 0) {                    if (e instanceof ForwardingNode) {                        tab = ((ForwardingNode<K,V>)e).nextTable;                        e = null;                        pushState(t, i, n);                        continue;                    }                    else if (e instanceof TreeBin)                        e = ((TreeBin<K,V>)e).first;                    else                        e = null;                }                if (stack != null)                    recoverState(n);                else if ((index = i + baseSize) >= n)                    index = ++baseIndex; // visit upper slots if present            }        }
        /**         * Saves traversal state upon encountering a forwarding node.         */        private void pushState(Node<K,V>[] t, int i, int n) {            TableStack<K,V> s = spare;  // reuse if possible            if (s != null)                spare = s.next;            else                s = new TableStack<K,V>();            s.tab = t;            s.length = n;            s.index = i;            s.next = stack;            stack = s;        }
        /**         * Possibly pops traversal state.         *         * @param n length of current table         */        private void recoverState(int n) {            TableStack<K,V> s; int len;            while ((s = stack) != null && (index += (len = s.length)) >= n) {                n = len;                index = s.index;                tab = s.tab;                s.tab = null;                TableStack<K,V> next = s.next;                s.next = spare; // save for reuse                stack = next;                spare = s;            }            if (s == null && (index += baseSize) >= n)                index = ++baseIndex;        }    }
    /**     * Base of key, value, and entry Iterators. Adds fields to     * Traverser to support iterator.remove.     */    static class BaseIterator<K,V> extends Traverser<K,V> {        final ConcurrentHashMap<K,V> map;        Node<K,V> lastReturned;        BaseIterator(Node<K,V>[] tab, int size, int index, int limit,                    ConcurrentHashMap<K,V> map) {            super(tab, size, index, limit);            this.map = map;            advance();        }
        public final boolean hasNext() { return next != null; }        public final boolean hasMoreElements() { return next != null; }
        public final void remove() {            Node<K,V> p;            if ((p = lastReturned) == null)                throw new IllegalStateException();            lastReturned = null;            map.replaceNode(p.key, null, null);        }    }
    static final class KeyIterator<K,V> extends BaseIterator<K,V>        implements Iterator<K>, Enumeration<K> {        KeyIterator(Node<K,V>[] tab, int index, int size, int limit,                    ConcurrentHashMap<K,V> map) {            super(tab, index, size, limit, map);        }
        public final K next() {            Node<K,V> p;            if ((p = next) == null)                throw new NoSuchElementException();            K k = p.key;            lastReturned = p;            advance();            return k;        }
        public final K nextElement() { return next(); }    }
    static final class ValueIterator<K,V> extends BaseIterator<K,V>        implements Iterator<V>, Enumeration<V> {        ValueIterator(Node<K,V>[] tab, int index, int size, int limit,                      ConcurrentHashMap<K,V> map) {            super(tab, index, size, limit, map);        }
        public final V next() {            Node<K,V> p;            if ((p = next) == null)                throw new NoSuchElementException();            V v = p.val;            lastReturned = p;            advance();            return v;        }
        public final V nextElement() { return next(); }    }
    static final class EntryIterator<K,V> extends BaseIterator<K,V>        implements Iterator<Map.Entry<K,V>> {        EntryIterator(Node<K,V>[] tab, int index, int size, int limit,                      ConcurrentHashMap<K,V> map) {            super(tab, index, size, limit, map);        }
        public final Map.Entry<K,V> next() {            Node<K,V> p;            if ((p = next) == null)                throw new NoSuchElementException();            K k = p.key;            V v = p.val;            lastReturned = p;            advance();            return new MapEntry<K,V>(k, v, map);        }    }
    /**     * Exported Entry for EntryIterator     */    static final class MapEntry<K,V> implements Map.Entry<K,V> {        final K key; // non-null        V val;       // non-null        final ConcurrentHashMap<K,V> map;        MapEntry(K key, V val, ConcurrentHashMap<K,V> map) {            this.key = key;            this.val = val;            this.map = map;        }        public K getKey()        { return key; }        public V getValue()      { return val; }        public int hashCode()    { return key.hashCode() ^ val.hashCode(); }        public String toString() { return key + "=" + val; }
        public boolean equals(Object o) {            Object k, v; Map.Entry<?,?> e;            return ((o instanceof Map.Entry) &&                    (k = (e = (Map.Entry<?,?>)o).getKey()) != null &&                    (v = e.getValue()) != null &&                    (k == key || k.equals(key)) &&                    (v == val || v.equals(val)));        }
        /**         * Sets our entry's value and writes through to the map. The         * value to return is somewhat arbitrary here. Since we do not         * necessarily track asynchronous changes, the most recent         * "previous" value could be different from what we return (or         * could even have been removed, in which case the put will         * re-establish). We do not and cannot guarantee more.         */        public V setValue(V value) {            if (value == null) throw new NullPointerException();            V v = val;            val = value;            map.put(key, value);            return v;        }    }
    static final class KeySpliterator<K,V> extends Traverser<K,V>        implements Spliterator<K> {        long est;               // size estimate        KeySpliterator(Node<K,V>[] tab, int size, int index, int limit,                       long est) {            super(tab, size, index, limit);            this.est = est;        }
        public Spliterator<K> trySplit() {            int i, f, h;            return (h = ((i = baseIndex) + (f = baseLimit)) >>> 1) <= i ? null :                new KeySpliterator<K,V>(tab, baseSize, baseLimit = h,                                        f, est >>>= 1);        }
        public void forEachRemaining(Consumer<? super K> action) {            if (action == null) throw new NullPointerException();            for (Node<K,V> p; (p = advance()) != null;)                action.accept(p.key);        }
        public boolean tryAdvance(Consumer<? super K> action) {            if (action == null) throw new NullPointerException();            Node<K,V> p;            if ((p = advance()) == null)                return false;            action.accept(p.key);            return true;        }
        public long estimateSize() { return est; }
        public int characteristics() {            return Spliterator.DISTINCT | Spliterator.CONCURRENT |                Spliterator.NONNULL;        }    }
    static final class ValueSpliterator<K,V> extends Traverser<K,V>        implements Spliterator<V> {        long est;               // size estimate        ValueSpliterator(Node<K,V>[] tab, int size, int index, int limit,                         long est) {            super(tab, size, index, limit);            this.est = est;        }
        public Spliterator<V> trySplit() {            int i, f, h;            return (h = ((i = baseIndex) + (f = baseLimit)) >>> 1) <= i ? null :                new ValueSpliterator<K,V>(tab, baseSize, baseLimit = h,                                          f, est >>>= 1);        }
        public void forEachRemaining(Consumer<? super V> action) {            if (action == null) throw new NullPointerException();            for (Node<K,V> p; (p = advance()) != null;)                action.accept(p.val);        }
        public boolean tryAdvance(Consumer<? super V> action) {            if (action == null) throw new NullPointerException();            Node<K,V> p;            if ((p = advance()) == null)                return false;            action.accept(p.val);            return true;        }
        public long estimateSize() { return est; }
        public int characteristics() {            return Spliterator.CONCURRENT | Spliterator.NONNULL;        }    }
    static final class EntrySpliterator<K,V> extends Traverser<K,V>        implements Spliterator<Map.Entry<K,V>> {        final ConcurrentHashMap<K,V> map; // To export MapEntry        long est;               // size estimate        EntrySpliterator(Node<K,V>[] tab, int size, int index, int limit,                         long est, ConcurrentHashMap<K,V> map) {            super(tab, size, index, limit);            this.map = map;            this.est = est;        }
        public Spliterator<Map.Entry<K,V>> trySplit() {            int i, f, h;            return (h = ((i = baseIndex) + (f = baseLimit)) >>> 1) <= i ? null :                new EntrySpliterator<K,V>(tab, baseSize, baseLimit = h,                                          f, est >>>= 1, map);        }
        public void forEachRemaining(Consumer<? super Map.Entry<K,V>> action) {            if (action == null) throw new NullPointerException();            for (Node<K,V> p; (p = advance()) != null; )                action.accept(new MapEntry<K,V>(p.key, p.val, map));        }
        public boolean tryAdvance(Consumer<? super Map.Entry<K,V>> action) {            if (action == null) throw new NullPointerException();            Node<K,V> p;            if ((p = advance()) == null)                return false;            action.accept(new MapEntry<K,V>(p.key, p.val, map));            return true;        }
        public long estimateSize() { return est; }
        public int characteristics() {            return Spliterator.DISTINCT | Spliterator.CONCURRENT |                Spliterator.NONNULL;        }    }
    // Parallel bulk operations
    /**     * Computes initial batch value for bulk tasks. The returned value     * is approximately exp2 of the number of times (minus one) to     * split task by two before executing leaf action. This value is     * faster to compute and more convenient to use as a guide to     * splitting than is the depth, since it is used while dividing by     * two anyway.     */    final int batchFor(long b) {        long n;        if (b == Long.MAX_VALUE || (n = sumCount()) <= 1L || n < b)            return 0;        int sp = ForkJoinPool.getCommonPoolParallelism() << 2; // slack of 4        return (b <= 0L || (n /= b) >= sp) ? sp : (int)n;    }
    /**     * Performs the given action for each (key, value).     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param action the action     * @since 1.8     */    public void forEach(long parallelismThreshold,                        BiConsumer<? super K,? super V> action) {        if (action == null) throw new NullPointerException();        new ForEachMappingTask<K,V>            (null, batchFor(parallelismThreshold), 0, 0, table,             action).invoke();    }
    /**     * Performs the given action for each non-null transformation     * of each (key, value).     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param transformer a function returning the transformation     * for an element, or null if there is no transformation (in     * which case the action is not applied)     * @param action the action     * @param <U> the return type of the transformer     * @since 1.8     */    public <U> void forEach(long parallelismThreshold,                            BiFunction<? super K, ? super V, ? extends U> transformer,                            Consumer<? super U> action) {        if (transformer == null || action == null)            throw new NullPointerException();        new ForEachTransformedMappingTask<K,V,U>            (null, batchFor(parallelismThreshold), 0, 0, table,             transformer, action).invoke();    }
    /**     * Returns a non-null result from applying the given search     * function on each (key, value), or null if none.  Upon     * success, further element processing is suppressed and the     * results of any other parallel invocations of the search     * function are ignored.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param searchFunction a function returning a non-null     * result on success, else null     * @param <U> the return type of the search function     * @return a non-null result from applying the given search     * function on each (key, value), or null if none     * @since 1.8     */    public <U> U search(long parallelismThreshold,                        BiFunction<? super K, ? super V, ? extends U> searchFunction) {        if (searchFunction == null) throw new NullPointerException();        return new SearchMappingsTask<K,V,U>            (null, batchFor(parallelismThreshold), 0, 0, table,             searchFunction, new AtomicReference<U>()).invoke();    }
    /**     * Returns the result of accumulating the given transformation     * of all (key, value) pairs using the given reducer to     * combine values, or null if none.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param transformer a function returning the transformation     * for an element, or null if there is no transformation (in     * which case it is not combined)     * @param reducer a commutative associative combining function     * @param <U> the return type of the transformer     * @return the result of accumulating the given transformation     * of all (key, value) pairs     * @since 1.8     */    public <U> U reduce(long parallelismThreshold,                        BiFunction<? super K, ? super V, ? extends U> transformer,                        BiFunction<? super U, ? super U, ? extends U> reducer) {        if (transformer == null || reducer == null)            throw new NullPointerException();        return new MapReduceMappingsTask<K,V,U>            (null, batchFor(parallelismThreshold), 0, 0, table,             null, transformer, reducer).invoke();    }
    /**     * Returns the result of accumulating the given transformation     * of all (key, value) pairs using the given reducer to     * combine values, and the given basis as an identity value.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param transformer a function returning the transformation     * for an element     * @param basis the identity (initial default value) for the reduction     * @param reducer a commutative associative combining function     * @return the result of accumulating the given transformation     * of all (key, value) pairs     * @since 1.8     */    public double reduceToDouble(long parallelismThreshold,                                 ToDoubleBiFunction<? super K, ? super V> transformer,                                 double basis,                                 DoubleBinaryOperator reducer) {        if (transformer == null || reducer == null)            throw new NullPointerException();        return new MapReduceMappingsToDoubleTask<K,V>            (null, batchFor(parallelismThreshold), 0, 0, table,             null, transformer, basis, reducer).invoke();    }
    /**     * Returns the result of accumulating the given transformation     * of all (key, value) pairs using the given reducer to     * combine values, and the given basis as an identity value.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param transformer a function returning the transformation     * for an element     * @param basis the identity (initial default value) for the reduction     * @param reducer a commutative associative combining function     * @return the result of accumulating the given transformation     * of all (key, value) pairs     * @since 1.8     */    public long reduceToLong(long parallelismThreshold,                             ToLongBiFunction<? super K, ? super V> transformer,                             long basis,                             LongBinaryOperator reducer) {        if (transformer == null || reducer == null)            throw new NullPointerException();        return new MapReduceMappingsToLongTask<K,V>            (null, batchFor(parallelismThreshold), 0, 0, table,             null, transformer, basis, reducer).invoke();    }
    /**     * Returns the result of accumulating the given transformation     * of all (key, value) pairs using the given reducer to     * combine values, and the given basis as an identity value.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param transformer a function returning the transformation     * for an element     * @param basis the identity (initial default value) for the reduction     * @param reducer a commutative associative combining function     * @return the result of accumulating the given transformation     * of all (key, value) pairs     * @since 1.8     */    public int reduceToInt(long parallelismThreshold,                           ToIntBiFunction<? super K, ? super V> transformer,                           int basis,                           IntBinaryOperator reducer) {        if (transformer == null || reducer == null)            throw new NullPointerException();        return new MapReduceMappingsToIntTask<K,V>            (null, batchFor(parallelismThreshold), 0, 0, table,             null, transformer, basis, reducer).invoke();    }
    /**     * Performs the given action for each key.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param action the action     * @since 1.8     */    public void forEachKey(long parallelismThreshold,                           Consumer<? super K> action) {        if (action == null) throw new NullPointerException();        new ForEachKeyTask<K,V>            (null, batchFor(parallelismThreshold), 0, 0, table,             action).invoke();    }
    /**     * Performs the given action for each non-null transformation     * of each key.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param transformer a function returning the transformation     * for an element, or null if there is no transformation (in     * which case the action is not applied)     * @param action the action     * @param <U> the return type of the transformer     * @since 1.8     */    public <U> void forEachKey(long parallelismThreshold,                               Function<? super K, ? extends U> transformer,                               Consumer<? super U> action) {        if (transformer == null || action == null)            throw new NullPointerException();        new ForEachTransformedKeyTask<K,V,U>            (null, batchFor(parallelismThreshold), 0, 0, table,             transformer, action).invoke();    }
    /**     * Returns a non-null result from applying the given search     * function on each key, or null if none. Upon success,     * further element processing is suppressed and the results of     * any other parallel invocations of the search function are     * ignored.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param searchFunction a function returning a non-null     * result on success, else null     * @param <U> the return type of the search function     * @return a non-null result from applying the given search     * function on each key, or null if none     * @since 1.8     */    public <U> U searchKeys(long parallelismThreshold,                            Function<? super K, ? extends U> searchFunction) {        if (searchFunction == null) throw new NullPointerException();        return new SearchKeysTask<K,V,U>            (null, batchFor(parallelismThreshold), 0, 0, table,             searchFunction, new AtomicReference<U>()).invoke();    }
    /**     * Returns the result of accumulating all keys using the given     * reducer to combine values, or null if none.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param reducer a commutative associative combining function     * @return the result of accumulating all keys using the given     * reducer to combine values, or null if none     * @since 1.8     */    public K reduceKeys(long parallelismThreshold,                        BiFunction<? super K, ? super K, ? extends K> reducer) {        if (reducer == null) throw new NullPointerException();        return new ReduceKeysTask<K,V>            (null, batchFor(parallelismThreshold), 0, 0, table,             null, reducer).invoke();    }
    /**     * Returns the result of accumulating the given transformation     * of all keys using the given reducer to combine values, or     * null if none.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param transformer a function returning the transformation     * for an element, or null if there is no transformation (in     * which case it is not combined)     * @param reducer a commutative associative combining function     * @param <U> the return type of the transformer     * @return the result of accumulating the given transformation     * of all keys     * @since 1.8     */    public <U> U reduceKeys(long parallelismThreshold,                            Function<? super K, ? extends U> transformer,         BiFunction<? super U, ? super U, ? extends U> reducer) {        if (transformer == null || reducer == null)            throw new NullPointerException();        return new MapReduceKeysTask<K,V,U>            (null, batchFor(parallelismThreshold), 0, 0, table,             null, transformer, reducer).invoke();    }
    /**     * Returns the result of accumulating the given transformation     * of all keys using the given reducer to combine values, and     * the given basis as an identity value.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param transformer a function returning the transformation     * for an element     * @param basis the identity (initial default value) for the reduction     * @param reducer a commutative associative combining function     * @return the result of accumulating the given transformation     * of all keys     * @since 1.8     */    public double reduceKeysToDouble(long parallelismThreshold,                                     ToDoubleFunction<? super K> transformer,                                     double basis,                                     DoubleBinaryOperator reducer) {        if (transformer == null || reducer == null)            throw new NullPointerException();        return new MapReduceKeysToDoubleTask<K,V>            (null, batchFor(parallelismThreshold), 0, 0, table,             null, transformer, basis, reducer).invoke();    }
    /**     * Returns the result of accumulating the given transformation     * of all keys using the given reducer to combine values, and     * the given basis as an identity value.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param transformer a function returning the transformation     * for an element     * @param basis the identity (initial default value) for the reduction     * @param reducer a commutative associative combining function     * @return the result of accumulating the given transformation     * of all keys     * @since 1.8     */    public long reduceKeysToLong(long parallelismThreshold,                                 ToLongFunction<? super K> transformer,                                 long basis,                                 LongBinaryOperator reducer) {        if (transformer == null || reducer == null)            throw new NullPointerException();        return new MapReduceKeysToLongTask<K,V>            (null, batchFor(parallelismThreshold), 0, 0, table,             null, transformer, basis, reducer).invoke();    }
    /**     * Returns the result of accumulating the given transformation     * of all keys using the given reducer to combine values, and     * the given basis as an identity value.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param transformer a function returning the transformation     * for an element     * @param basis the identity (initial default value) for the reduction     * @param reducer a commutative associative combining function     * @return the result of accumulating the given transformation     * of all keys     * @since 1.8     */    public int reduceKeysToInt(long parallelismThreshold,                               ToIntFunction<? super K> transformer,                               int basis,                               IntBinaryOperator reducer) {        if (transformer == null || reducer == null)            throw new NullPointerException();        return new MapReduceKeysToIntTask<K,V>            (null, batchFor(parallelismThreshold), 0, 0, table,             null, transformer, basis, reducer).invoke();    }
    /**     * Performs the given action for each value.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param action the action     * @since 1.8     */    public void forEachValue(long parallelismThreshold,                             Consumer<? super V> action) {        if (action == null)            throw new NullPointerException();        new ForEachValueTask<K,V>            (null, batchFor(parallelismThreshold), 0, 0, table,             action).invoke();    }
    /**     * Performs the given action for each non-null transformation     * of each value.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param transformer a function returning the transformation     * for an element, or null if there is no transformation (in     * which case the action is not applied)     * @param action the action     * @param <U> the return type of the transformer     * @since 1.8     */    public <U> void forEachValue(long parallelismThreshold,                                 Function<? super V, ? extends U> transformer,                                 Consumer<? super U> action) {        if (transformer == null || action == null)            throw new NullPointerException();        new ForEachTransformedValueTask<K,V,U>            (null, batchFor(parallelismThreshold), 0, 0, table,             transformer, action).invoke();    }
    /**     * Returns a non-null result from applying the given search     * function on each value, or null if none.  Upon success,     * further element processing is suppressed and the results of     * any other parallel invocations of the search function are     * ignored.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param searchFunction a function returning a non-null     * result on success, else null     * @param <U> the return type of the search function     * @return a non-null result from applying the given search     * function on each value, or null if none     * @since 1.8     */    public <U> U searchValues(long parallelismThreshold,                              Function<? super V, ? extends U> searchFunction) {        if (searchFunction == null) throw new NullPointerException();        return new SearchValuesTask<K,V,U>            (null, batchFor(parallelismThreshold), 0, 0, table,             searchFunction, new AtomicReference<U>()).invoke();    }
    /**     * Returns the result of accumulating all values using the     * given reducer to combine values, or null if none.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param reducer a commutative associative combining function     * @return the result of accumulating all values     * @since 1.8     */    public V reduceValues(long parallelismThreshold,                          BiFunction<? super V, ? super V, ? extends V> reducer) {        if (reducer == null) throw new NullPointerException();        return new ReduceValuesTask<K,V>            (null, batchFor(parallelismThreshold), 0, 0, table,             null, reducer).invoke();    }
    /**     * Returns the result of accumulating the given transformation     * of all values using the given reducer to combine values, or     * null if none.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param transformer a function returning the transformation     * for an element, or null if there is no transformation (in     * which case it is not combined)     * @param reducer a commutative associative combining function     * @param <U> the return type of the transformer     * @return the result of accumulating the given transformation     * of all values     * @since 1.8     */    public <U> U reduceValues(long parallelismThreshold,                              Function<? super V, ? extends U> transformer,                              BiFunction<? super U, ? super U, ? extends U> reducer) {        if (transformer == null || reducer == null)            throw new NullPointerException();        return new MapReduceValuesTask<K,V,U>            (null, batchFor(parallelismThreshold), 0, 0, table,             null, transformer, reducer).invoke();    }
    /**     * Returns the result of accumulating the given transformation     * of all values using the given reducer to combine values,     * and the given basis as an identity value.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param transformer a function returning the transformation     * for an element     * @param basis the identity (initial default value) for the reduction     * @param reducer a commutative associative combining function     * @return the result of accumulating the given transformation     * of all values     * @since 1.8     */    public double reduceValuesToDouble(long parallelismThreshold,                                       ToDoubleFunction<? super V> transformer,                                       double basis,                                       DoubleBinaryOperator reducer) {        if (transformer == null || reducer == null)            throw new NullPointerException();        return new MapReduceValuesToDoubleTask<K,V>            (null, batchFor(parallelismThreshold), 0, 0, table,             null, transformer, basis, reducer).invoke();    }
    /**     * Returns the result of accumulating the given transformation     * of all values using the given reducer to combine values,     * and the given basis as an identity value.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param transformer a function returning the transformation     * for an element     * @param basis the identity (initial default value) for the reduction     * @param reducer a commutative associative combining function     * @return the result of accumulating the given transformation     * of all values     * @since 1.8     */    public long reduceValuesToLong(long parallelismThreshold,                                   ToLongFunction<? super V> transformer,                                   long basis,                                   LongBinaryOperator reducer) {        if (transformer == null || reducer == null)            throw new NullPointerException();        return new MapReduceValuesToLongTask<K,V>            (null, batchFor(parallelismThreshold), 0, 0, table,             null, transformer, basis, reducer).invoke();    }
    /**     * Returns the result of accumulating the given transformation     * of all values using the given reducer to combine values,     * and the given basis as an identity value.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param transformer a function returning the transformation     * for an element     * @param basis the identity (initial default value) for the reduction     * @param reducer a commutative associative combining function     * @return the result of accumulating the given transformation     * of all values     * @since 1.8     */    public int reduceValuesToInt(long parallelismThreshold,                                 ToIntFunction<? super V> transformer,                                 int basis,                                 IntBinaryOperator reducer) {        if (transformer == null || reducer == null)            throw new NullPointerException();        return new MapReduceValuesToIntTask<K,V>            (null, batchFor(parallelismThreshold), 0, 0, table,             null, transformer, basis, reducer).invoke();    }
    /**     * Performs the given action for each entry.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param action the action     * @since 1.8     */    public void forEachEntry(long parallelismThreshold,                             Consumer<? super Map.Entry<K,V>> action) {        if (action == null) throw new NullPointerException();        new ForEachEntryTask<K,V>(null, batchFor(parallelismThreshold), 0, 0, table,                                  action).invoke();    }
    /**     * Performs the given action for each non-null transformation     * of each entry.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param transformer a function returning the transformation     * for an element, or null if there is no transformation (in     * which case the action is not applied)     * @param action the action     * @param <U> the return type of the transformer     * @since 1.8     */    public <U> void forEachEntry(long parallelismThreshold,                                 Function<Map.Entry<K,V>, ? extends U> transformer,                                 Consumer<? super U> action) {        if (transformer == null || action == null)            throw new NullPointerException();        new ForEachTransformedEntryTask<K,V,U>            (null, batchFor(parallelismThreshold), 0, 0, table,             transformer, action).invoke();    }
    /**     * Returns a non-null result from applying the given search     * function on each entry, or null if none.  Upon success,     * further element processing is suppressed and the results of     * any other parallel invocations of the search function are     * ignored.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param searchFunction a function returning a non-null     * result on success, else null     * @param <U> the return type of the search function     * @return a non-null result from applying the given search     * function on each entry, or null if none     * @since 1.8     */    public <U> U searchEntries(long parallelismThreshold,                               Function<Map.Entry<K,V>, ? extends U> searchFunction) {        if (searchFunction == null) throw new NullPointerException();        return new SearchEntriesTask<K,V,U>            (null, batchFor(parallelismThreshold), 0, 0, table,             searchFunction, new AtomicReference<U>()).invoke();    }
    /**     * Returns the result of accumulating all entries using the     * given reducer to combine values, or null if none.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param reducer a commutative associative combining function     * @return the result of accumulating all entries     * @since 1.8     */    public Map.Entry<K,V> reduceEntries(long parallelismThreshold,                                        BiFunction<Map.Entry<K,V>, Map.Entry<K,V>, ? extends Map.Entry<K,V>> reducer) {        if (reducer == null) throw new NullPointerException();        return new ReduceEntriesTask<K,V>            (null, batchFor(parallelismThreshold), 0, 0, table,             null, reducer).invoke();    }
    /**     * Returns the result of accumulating the given transformation     * of all entries using the given reducer to combine values,     * or null if none.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param transformer a function returning the transformation     * for an element, or null if there is no transformation (in     * which case it is not combined)     * @param reducer a commutative associative combining function     * @param <U> the return type of the transformer     * @return the result of accumulating the given transformation     * of all entries     * @since 1.8     */    public <U> U reduceEntries(long parallelismThreshold,                               Function<Map.Entry<K,V>, ? extends U> transformer,                               BiFunction<? super U, ? super U, ? extends U> reducer) {        if (transformer == null || reducer == null)            throw new NullPointerException();        return new MapReduceEntriesTask<K,V,U>            (null, batchFor(parallelismThreshold), 0, 0, table,             null, transformer, reducer).invoke();    }
    /**     * Returns the result of accumulating the given transformation     * of all entries using the given reducer to combine values,     * and the given basis as an identity value.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param transformer a function returning the transformation     * for an element     * @param basis the identity (initial default value) for the reduction     * @param reducer a commutative associative combining function     * @return the result of accumulating the given transformation     * of all entries     * @since 1.8     */    public double reduceEntriesToDouble(long parallelismThreshold,                                        ToDoubleFunction<Map.Entry<K,V>> transformer,                                        double basis,                                        DoubleBinaryOperator reducer) {        if (transformer == null || reducer == null)            throw new NullPointerException();        return new MapReduceEntriesToDoubleTask<K,V>            (null, batchFor(parallelismThreshold), 0, 0, table,             null, transformer, basis, reducer).invoke();    }
    /**     * Returns the result of accumulating the given transformation     * of all entries using the given reducer to combine values,     * and the given basis as an identity value.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param transformer a function returning the transformation     * for an element     * @param basis the identity (initial default value) for the reduction     * @param reducer a commutative associative combining function     * @return the result of accumulating the given transformation     * of all entries     * @since 1.8     */    public long reduceEntriesToLong(long parallelismThreshold,                                    ToLongFunction<Map.Entry<K,V>> transformer,                                    long basis,                                    LongBinaryOperator reducer) {        if (transformer == null || reducer == null)            throw new NullPointerException();        return new MapReduceEntriesToLongTask<K,V>            (null, batchFor(parallelismThreshold), 0, 0, table,             null, transformer, basis, reducer).invoke();    }
    /**     * Returns the result of accumulating the given transformation     * of all entries using the given reducer to combine values,     * and the given basis as an identity value.     *     * @param parallelismThreshold the (estimated) number of elements     * needed for this operation to be executed in parallel     * @param transformer a function returning the transformation     * for an element     * @param basis the identity (initial default value) for the reduction     * @param reducer a commutative associative combining function     * @return the result of accumulating the given transformation     * of all entries     * @since 1.8     */    public int reduceEntriesToInt(long parallelismThreshold,                                  ToIntFunction<Map.Entry<K,V>> transformer,                                  int basis,                                  IntBinaryOperator reducer) {        if (transformer == null || reducer == null)            throw new NullPointerException();        return new MapReduceEntriesToIntTask<K,V>            (null, batchFor(parallelismThreshold), 0, 0, table,             null, transformer, basis, reducer).invoke();    }

    /* ----------------Views -------------- */
    /**     * Base class for views.     */    abstract static class CollectionView<K,V,E>        implements Collection<E>, java.io.Serializable {        private static final long serialVersionUID = 7249069246763182397L;        final ConcurrentHashMap<K,V> map;        CollectionView(ConcurrentHashMap<K,V> map)  { this.map = map; }
        /**         * Returns the map backing this view.         *         * @return the map backing this view         */        public ConcurrentHashMap<K,V> getMap() { return map; }
        /**         * Removes all of the elements from this view, by removing all         * the mappings from the map backing this view.         */        public final void clear()      { map.clear(); }        public final int size()        { return map.size(); }        public final boolean isEmpty() { return map.isEmpty(); }
        // implementations below rely on concrete classes supplying these        // abstract methods        /**         * Returns an iterator over the elements in this collection.         *         * <p>The returned iterator is         * <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>.         *         * @return an iterator over the elements in this collection         */        public abstract Iterator<E> iterator();        public abstract boolean contains(Object o);        public abstract boolean remove(Object o);
        private static final String oomeMsg = "Required array size too large";
        public final Object[] toArray() {            long sz = map.mappingCount();            if (sz > MAX_ARRAY_SIZE)                throw new OutOfMemoryError(oomeMsg);            int n = (int)sz;            Object[] r = new Object[n];            int i = 0;            for (E e : this) {                if (i == n) {                    if (n >= MAX_ARRAY_SIZE)                        throw new OutOfMemoryError(oomeMsg);                    if (n >= MAX_ARRAY_SIZE - (MAX_ARRAY_SIZE >>> 1) - 1)                        n = MAX_ARRAY_SIZE;                    else                        n += (n >>> 1) + 1;                    r = Arrays.copyOf(r, n);                }                r[i++] = e;            }            return (i == n) ? r : Arrays.copyOf(r, i);        }
        @SuppressWarnings("unchecked")        public final <T> T[] toArray(T[] a) {            long sz = map.mappingCount();            if (sz > MAX_ARRAY_SIZE)                throw new OutOfMemoryError(oomeMsg);            int m = (int)sz;            T[] r = (a.length >= m) ? a :                (T[])java.lang.reflect.Array                .newInstance(a.getClass().getComponentType(), m);            int n = r.length;            int i = 0;            for (E e : this) {                if (i == n) {                    if (n >= MAX_ARRAY_SIZE)                        throw new OutOfMemoryError(oomeMsg);                    if (n >= MAX_ARRAY_SIZE - (MAX_ARRAY_SIZE >>> 1) - 1)                        n = MAX_ARRAY_SIZE;                    else                        n += (n >>> 1) + 1;                    r = Arrays.copyOf(r, n);                }                r[i++] = (T)e;            }            if (a == r && i < n) {                r[i] = null; // null-terminate                return r;            }            return (i == n) ? r : Arrays.copyOf(r, i);        }
        /**         * Returns a string representation of this collection.         * The string representation consists of the string representations         * of the collection's elements in the order they are returned by         * its iterator, enclosed in square brackets ({@code "[]"}).         * Adjacent elements are separated by the characters {@code ", "}         * (comma and space).  Elements are converted to strings as by         * {@link String#valueOf(Object)}.         *         * @return a string representation of this collection         */        public final String toString() {            StringBuilder sb = new StringBuilder();            sb.append('[');            Iterator<E> it = iterator();            if (it.hasNext()) {                for (;;) {                    Object e = it.next();                    sb.append(e == this ? "(this Collection)" : e);                    if (!it.hasNext())                        break;                    sb.append(',').append(' ');                }            }            return sb.append(']').toString();        }
        public final boolean containsAll(Collection<?> c) {            if (c != this) {                for (Object e : c) {                    if (e == null || !contains(e))                        return false;                }            }            return true;        }
        public final boolean removeAll(Collection<?> c) {            if (c == null) throw new NullPointerException();            boolean modified = false;            for (Iterator<E> it = iterator(); it.hasNext();) {                if (c.contains(it.next())) {                    it.remove();                    modified = true;                }            }            return modified;        }
        public final boolean retainAll(Collection<?> c) {            if (c == null) throw new NullPointerException();            boolean modified = false;            for (Iterator<E> it = iterator(); it.hasNext();) {                if (!c.contains(it.next())) {                    it.remove();                    modified = true;                }            }            return modified;        }
    }
    /**     * A view of a ConcurrentHashMap as a {@link Set} of keys, in     * which additions may optionally be enabled by mapping to a     * common value.  This class cannot be directly instantiated.     * See {@link #keySet() keySet()},     * {@link #keySet(Object) keySet(V)},     * {@link #newKeySet() newKeySet()},     * {@link #newKeySet(int) newKeySet(int)}.     *     * @since 1.8     */    public static class KeySetView<K,V> extends CollectionView<K,V,K>        implements Set<K>, java.io.Serializable {        private static final long serialVersionUID = 7249069246763182397L;        private final V value;        KeySetView(ConcurrentHashMap<K,V> map, V value) {  // non-public            super(map);            this.value = value;        }
        /**         * Returns the default mapped value for additions,         * or {@code null} if additions are not supported.         *         * @return the default mapped value for additions, or {@code null}         * if not supported         */        public V getMappedValue() { return value; }
        /**         * {@inheritDoc}         * @throws NullPointerException if the specified key is null         */        public boolean contains(Object o) { return map.containsKey(o); }
        /**         * Removes the key from this map view, by removing the key (and its         * corresponding value) from the backing map.  This method does         * nothing if the key is not in the map.         *         * @param  o the key to be removed from the backing map         * @return {@code true} if the backing map contained the specified key         * @throws NullPointerException if the specified key is null         */        public boolean remove(Object o) { return map.remove(o) != null; }
        /**         * @return an iterator over the keys of the backing map         */        public Iterator<K> iterator() {            Node<K,V>[] t;            ConcurrentHashMap<K,V> m = map;            int f = (t = m.table) == null ? 0 : t.length;            return new KeyIterator<K,V>(t, f, 0, f, m);        }
        /**         * Adds the specified key to this set view by mapping the key to         * the default mapped value in the backing map, if defined.         *         * @param e key to be added         * @return {@code true} if this set changed as a result of the call         * @throws NullPointerException if the specified key is null         * @throws UnsupportedOperationException if no default mapped value         * for additions was provided         */        public boolean add(K e) {            V v;            if ((v = value) == null)                throw new UnsupportedOperationException();            return map.putVal(e, v, true) == null;        }
        /**         * Adds all of the elements in the specified collection to this set,         * as if by calling {@link #add} on each one.         *         * @param c the elements to be inserted into this set         * @return {@code true} if this set changed as a result of the call         * @throws NullPointerException if the collection or any of its         * elements are {@code null}         * @throws UnsupportedOperationException if no default mapped value         * for additions was provided         */        public boolean addAll(Collection<? extends K> c) {            boolean added = false;            V v;            if ((v = value) == null)                throw new UnsupportedOperationException();            for (K e : c) {                if (map.putVal(e, v, true) == null)                    added = true;            }            return added;        }
        public int hashCode() {            int h = 0;            for (K e : this)                h += e.hashCode();            return h;        }
        public boolean equals(Object o) {            Set<?> c;            return ((o instanceof Set) &&                    ((c = (Set<?>)o) == this ||                     (containsAll(c) && c.containsAll(this))));        }
        public Spliterator<K> spliterator() {            Node<K,V>[] t;            ConcurrentHashMap<K,V> m = map;            long n = m.sumCount();            int f = (t = m.table) == null ? 0 : t.length;            return new KeySpliterator<K,V>(t, f, 0, f, n < 0L ? 0L : n);        }
        public void forEach(Consumer<? super K> action) {            if (action == null) throw new NullPointerException();            Node<K,V>[] t;            if ((t = map.table) != null) {                Traverser<K,V> it = new Traverser<K,V>(t, t.length, 0, t.length);                for (Node<K,V> p; (p = it.advance()) != null; )                    action.accept(p.key);            }        }    }
    /**     * A view of a ConcurrentHashMap as a {@link Collection} of     * values, in which additions are disabled. This class cannot be     * directly instantiated. See {@link #values()}.     */    static final class ValuesView<K,V> extends CollectionView<K,V,V>        implements Collection<V>, java.io.Serializable {        private static final long serialVersionUID = 2249069246763182397L;        ValuesView(ConcurrentHashMap<K,V> map) { super(map); }        public final boolean contains(Object o) {            return map.containsValue(o);        }
        public final boolean remove(Object o) {            if (o != null) {                for (Iterator<V> it = iterator(); it.hasNext();) {                    if (o.equals(it.next())) {                        it.remove();                        return true;                    }                }            }            return false;        }
        public final Iterator<V> iterator() {            ConcurrentHashMap<K,V> m = map;            Node<K,V>[] t;            int f = (t = m.table) == null ? 0 : t.length;            return new ValueIterator<K,V>(t, f, 0, f, m);        }
        public final boolean add(V e) {            throw new UnsupportedOperationException();        }        public final boolean addAll(Collection<? extends V> c) {            throw new UnsupportedOperationException();        }
        public Spliterator<V> spliterator() {            Node<K,V>[] t;            ConcurrentHashMap<K,V> m = map;            long n = m.sumCount();            int f = (t = m.table) == null ? 0 : t.length;            return new ValueSpliterator<K,V>(t, f, 0, f, n < 0L ? 0L : n);        }
        public void forEach(Consumer<? super V> action) {            if (action == null) throw new NullPointerException();            Node<K,V>[] t;            if ((t = map.table) != null) {                Traverser<K,V> it = new Traverser<K,V>(t, t.length, 0, t.length);                for (Node<K,V> p; (p = it.advance()) != null; )                    action.accept(p.val);            }        }    }
    /**     * A view of a ConcurrentHashMap as a {@link Set} of (key, value)     * entries.  This class cannot be directly instantiated. See     * {@link #entrySet()}.     */    static final class EntrySetView<K,V> extends CollectionView<K,V,Map.Entry<K,V>>        implements Set<Map.Entry<K,V>>, java.io.Serializable {        private static final long serialVersionUID = 2249069246763182397L;        EntrySetView(ConcurrentHashMap<K,V> map) { super(map); }
        public boolean contains(Object o) {            Object k, v, r; Map.Entry<?,?> e;            return ((o instanceof Map.Entry) &&                    (k = (e = (Map.Entry<?,?>)o).getKey()) != null &&                    (r = map.get(k)) != null &&                    (v = e.getValue()) != null &&                    (v == r || v.equals(r)));        }
        public boolean remove(Object o) {            Object k, v; Map.Entry<?,?> e;            return ((o instanceof Map.Entry) &&                    (k = (e = (Map.Entry<?,?>)o).getKey()) != null &&                    (v = e.getValue()) != null &&                    map.remove(k, v));        }
        /**         * @return an iterator over the entries of the backing map         */        public Iterator<Map.Entry<K,V>> iterator() {            ConcurrentHashMap<K,V> m = map;            Node<K,V>[] t;            int f = (t = m.table) == null ? 0 : t.length;            return new EntryIterator<K,V>(t, f, 0, f, m);        }
        public boolean add(Entry<K,V> e) {            return map.putVal(e.getKey(), e.getValue(), false) == null;        }
        public boolean addAll(Collection<? extends Entry<K,V>> c) {            boolean added = false;            for (Entry<K,V> e : c) {                if (add(e))                    added = true;            }            return added;        }
        public final int hashCode() {            int h = 0;            Node<K,V>[] t;            if ((t = map.table) != null) {                Traverser<K,V> it = new Traverser<K,V>(t, t.length, 0, t.length);                for (Node<K,V> p; (p = it.advance()) != null; ) {                    h += p.hashCode();                }            }            return h;        }
        public final boolean equals(Object o) {            Set<?> c;            return ((o instanceof Set) &&                    ((c = (Set<?>)o) == this ||                     (containsAll(c) && c.containsAll(this))));        }
        public Spliterator<Map.Entry<K,V>> spliterator() {            Node<K,V>[] t;            ConcurrentHashMap<K,V> m = map;            long n = m.sumCount();            int f = (t = m.table) == null ? 0 : t.length;            return new EntrySpliterator<K,V>(t, f, 0, f, n < 0L ? 0L : n, m);        }
        public void forEach(Consumer<? super Map.Entry<K,V>> action) {            if (action == null) throw new NullPointerException();            Node<K,V>[] t;            if ((t = map.table) != null) {                Traverser<K,V> it = new Traverser<K,V>(t, t.length, 0, t.length);                for (Node<K,V> p; (p = it.advance()) != null; )                    action.accept(new MapEntry<K,V>(p.key, p.val, map));            }        }
    }
    // -------------------------------------------------------
    /**     * Base class for bulk tasks. Repeats some fields and code from     * class Traverser, because we need to subclass CountedCompleter.     */    @SuppressWarnings("serial")    abstract static class BulkTask<K,V,R> extends CountedCompleter<R> {        Node<K,V>[] tab;        // same as Traverser        Node<K,V> next;        TableStack<K,V> stack, spare;        int index;        int baseIndex;        int baseLimit;        final int baseSize;        int batch;              // split control
        BulkTask(BulkTask<K,V,?> par, int b, int i, int f, Node<K,V>[] t) {            super(par);            this.batch = b;            this.index = this.baseIndex = i;            if ((this.tab = t) == null)                this.baseSize = this.baseLimit = 0;            else if (par == null)                this.baseSize = this.baseLimit = t.length;            else {                this.baseLimit = f;                this.baseSize = par.baseSize;            }        }
        /**         * Same as Traverser version         */        final Node<K,V> advance() {            Node<K,V> e;            if ((e = next) != null)                e = e.next;            for (;;) {                Node<K,V>[] t; int i, n;                if (e != null)                    return next = e;                if (baseIndex >= baseLimit || (t = tab) == null ||                    (n = t.length) <= (i = index) || i < 0)                    return next = null;                if ((e = tabAt(t, i)) != null && e.hash < 0) {                    if (e instanceof ForwardingNode) {                        tab = ((ForwardingNode<K,V>)e).nextTable;                        e = null;                        pushState(t, i, n);                        continue;                    }                    else if (e instanceof TreeBin)                        e = ((TreeBin<K,V>)e).first;                    else                        e = null;                }                if (stack != null)                    recoverState(n);                else if ((index = i + baseSize) >= n)                    index = ++baseIndex;            }        }
        private void pushState(Node<K,V>[] t, int i, int n) {            TableStack<K,V> s = spare;            if (s != null)                spare = s.next;            else                s = new TableStack<K,V>();            s.tab = t;            s.length = n;            s.index = i;            s.next = stack;            stack = s;        }
        private void recoverState(int n) {            TableStack<K,V> s; int len;            while ((s = stack) != null && (index += (len = s.length)) >= n) {                n = len;                index = s.index;                tab = s.tab;                s.tab = null;                TableStack<K,V> next = s.next;                s.next = spare; // save for reuse                stack = next;                spare = s;            }            if (s == null && (index += baseSize) >= n)                index = ++baseIndex;        }    }
    /*     * Task classes. Coded in a regular but ugly format/style to     * simplify checks that each variant differs in the right way from     * others. The null screenings exist because compilers cannot tell     * that we've already null-checked task arguments, so we force     * simplest hoisted bypass to help avoid convoluted traps.     */    @SuppressWarnings("serial")    static final class ForEachKeyTask<K,V>        extends BulkTask<K,V,Void> {        final Consumer<? super K> action;        ForEachKeyTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             Consumer<? super K> action) {            super(p, b, i, f, t);            this.action = action;        }        public final void compute() {            final Consumer<? super K> action;            if ((action = this.action) != null) {                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    new ForEachKeyTask<K,V>                        (this, batch >>>= 1, baseLimit = h, f, tab,                         action).fork();                }                for (Node<K,V> p; (p = advance()) != null;)                    action.accept(p.key);                propagateCompletion();            }        }    }
    @SuppressWarnings("serial")    static final class ForEachValueTask<K,V>        extends BulkTask<K,V,Void> {        final Consumer<? super V> action;        ForEachValueTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             Consumer<? super V> action) {            super(p, b, i, f, t);            this.action = action;        }        public final void compute() {            final Consumer<? super V> action;            if ((action = this.action) != null) {                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    new ForEachValueTask<K,V>                        (this, batch >>>= 1, baseLimit = h, f, tab,                         action).fork();                }                for (Node<K,V> p; (p = advance()) != null;)                    action.accept(p.val);                propagateCompletion();            }        }    }
    @SuppressWarnings("serial")    static final class ForEachEntryTask<K,V>        extends BulkTask<K,V,Void> {        final Consumer<? super Entry<K,V>> action;        ForEachEntryTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             Consumer<? super Entry<K,V>> action) {            super(p, b, i, f, t);            this.action = action;        }        public final void compute() {            final Consumer<? super Entry<K,V>> action;            if ((action = this.action) != null) {                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    new ForEachEntryTask<K,V>                        (this, batch >>>= 1, baseLimit = h, f, tab,                         action).fork();                }                for (Node<K,V> p; (p = advance()) != null; )                    action.accept(p);                propagateCompletion();            }        }    }
    @SuppressWarnings("serial")    static final class ForEachMappingTask<K,V>        extends BulkTask<K,V,Void> {        final BiConsumer<? super K, ? super V> action;        ForEachMappingTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             BiConsumer<? super K,? super V> action) {            super(p, b, i, f, t);            this.action = action;        }        public final void compute() {            final BiConsumer<? super K, ? super V> action;            if ((action = this.action) != null) {                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    new ForEachMappingTask<K,V>                        (this, batch >>>= 1, baseLimit = h, f, tab,                         action).fork();                }                for (Node<K,V> p; (p = advance()) != null; )                    action.accept(p.key, p.val);                propagateCompletion();            }        }    }
    @SuppressWarnings("serial")    static final class ForEachTransformedKeyTask<K,V,U>        extends BulkTask<K,V,Void> {        final Function<? super K, ? extends U> transformer;        final Consumer<? super U> action;        ForEachTransformedKeyTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             Function<? super K, ? extends U> transformer, Consumer<? super U> action) {            super(p, b, i, f, t);            this.transformer = transformer; this.action = action;        }        public final void compute() {            final Function<? super K, ? extends U> transformer;            final Consumer<? super U> action;            if ((transformer = this.transformer) != null &&                (action = this.action) != null) {                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    new ForEachTransformedKeyTask<K,V,U>                        (this, batch >>>= 1, baseLimit = h, f, tab,                         transformer, action).fork();                }                for (Node<K,V> p; (p = advance()) != null; ) {                    U u;                    if ((u = transformer.apply(p.key)) != null)                        action.accept(u);                }                propagateCompletion();            }        }    }
    @SuppressWarnings("serial")    static final class ForEachTransformedValueTask<K,V,U>        extends BulkTask<K,V,Void> {        final Function<? super V, ? extends U> transformer;        final Consumer<? super U> action;        ForEachTransformedValueTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             Function<? super V, ? extends U> transformer, Consumer<? super U> action) {            super(p, b, i, f, t);            this.transformer = transformer; this.action = action;        }        public final void compute() {            final Function<? super V, ? extends U> transformer;            final Consumer<? super U> action;            if ((transformer = this.transformer) != null &&                (action = this.action) != null) {                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    new ForEachTransformedValueTask<K,V,U>                        (this, batch >>>= 1, baseLimit = h, f, tab,                         transformer, action).fork();                }                for (Node<K,V> p; (p = advance()) != null; ) {                    U u;                    if ((u = transformer.apply(p.val)) != null)                        action.accept(u);                }                propagateCompletion();            }        }    }
    @SuppressWarnings("serial")    static final class ForEachTransformedEntryTask<K,V,U>        extends BulkTask<K,V,Void> {        final Function<Map.Entry<K,V>, ? extends U> transformer;        final Consumer<? super U> action;        ForEachTransformedEntryTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             Function<Map.Entry<K,V>, ? extends U> transformer, Consumer<? super U> action) {            super(p, b, i, f, t);            this.transformer = transformer; this.action = action;        }        public final void compute() {            final Function<Map.Entry<K,V>, ? extends U> transformer;            final Consumer<? super U> action;            if ((transformer = this.transformer) != null &&                (action = this.action) != null) {                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    new ForEachTransformedEntryTask<K,V,U>                        (this, batch >>>= 1, baseLimit = h, f, tab,                         transformer, action).fork();                }                for (Node<K,V> p; (p = advance()) != null; ) {                    U u;                    if ((u = transformer.apply(p)) != null)                        action.accept(u);                }                propagateCompletion();            }        }    }
    @SuppressWarnings("serial")    static final class ForEachTransformedMappingTask<K,V,U>        extends BulkTask<K,V,Void> {        final BiFunction<? super K, ? super V, ? extends U> transformer;        final Consumer<? super U> action;        ForEachTransformedMappingTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             BiFunction<? super K, ? super V, ? extends U> transformer,             Consumer<? super U> action) {            super(p, b, i, f, t);            this.transformer = transformer; this.action = action;        }        public final void compute() {            final BiFunction<? super K, ? super V, ? extends U> transformer;            final Consumer<? super U> action;            if ((transformer = this.transformer) != null &&                (action = this.action) != null) {                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    new ForEachTransformedMappingTask<K,V,U>                        (this, batch >>>= 1, baseLimit = h, f, tab,                         transformer, action).fork();                }                for (Node<K,V> p; (p = advance()) != null; ) {                    U u;                    if ((u = transformer.apply(p.key, p.val)) != null)                        action.accept(u);                }                propagateCompletion();            }        }    }
    @SuppressWarnings("serial")    static final class SearchKeysTask<K,V,U>        extends BulkTask<K,V,U> {        final Function<? super K, ? extends U> searchFunction;        final AtomicReference<U> result;        SearchKeysTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             Function<? super K, ? extends U> searchFunction,             AtomicReference<U> result) {            super(p, b, i, f, t);            this.searchFunction = searchFunction; this.result = result;        }        public final U getRawResult() { return result.get(); }        public final void compute() {            final Function<? super K, ? extends U> searchFunction;            final AtomicReference<U> result;            if ((searchFunction = this.searchFunction) != null &&                (result = this.result) != null) {                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    if (result.get() != null)                        return;                    addToPendingCount(1);                    new SearchKeysTask<K,V,U>                        (this, batch >>>= 1, baseLimit = h, f, tab,                         searchFunction, result).fork();                }                while (result.get() == null) {                    U u;                    Node<K,V> p;                    if ((p = advance()) == null) {                        propagateCompletion();                        break;                    }                    if ((u = searchFunction.apply(p.key)) != null) {                        if (result.compareAndSet(null, u))                            quietlyCompleteRoot();                        break;                    }                }            }        }    }
    @SuppressWarnings("serial")    static final class SearchValuesTask<K,V,U>        extends BulkTask<K,V,U> {        final Function<? super V, ? extends U> searchFunction;        final AtomicReference<U> result;        SearchValuesTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             Function<? super V, ? extends U> searchFunction,             AtomicReference<U> result) {            super(p, b, i, f, t);            this.searchFunction = searchFunction; this.result = result;        }        public final U getRawResult() { return result.get(); }        public final void compute() {            final Function<? super V, ? extends U> searchFunction;            final AtomicReference<U> result;            if ((searchFunction = this.searchFunction) != null &&                (result = this.result) != null) {                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    if (result.get() != null)                        return;                    addToPendingCount(1);                    new SearchValuesTask<K,V,U>                        (this, batch >>>= 1, baseLimit = h, f, tab,                         searchFunction, result).fork();                }                while (result.get() == null) {                    U u;                    Node<K,V> p;                    if ((p = advance()) == null) {                        propagateCompletion();                        break;                    }                    if ((u = searchFunction.apply(p.val)) != null) {                        if (result.compareAndSet(null, u))                            quietlyCompleteRoot();                        break;                    }                }            }        }    }
    @SuppressWarnings("serial")    static final class SearchEntriesTask<K,V,U>        extends BulkTask<K,V,U> {        final Function<Entry<K,V>, ? extends U> searchFunction;        final AtomicReference<U> result;        SearchEntriesTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             Function<Entry<K,V>, ? extends U> searchFunction,             AtomicReference<U> result) {            super(p, b, i, f, t);            this.searchFunction = searchFunction; this.result = result;        }        public final U getRawResult() { return result.get(); }        public final void compute() {            final Function<Entry<K,V>, ? extends U> searchFunction;            final AtomicReference<U> result;            if ((searchFunction = this.searchFunction) != null &&                (result = this.result) != null) {                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    if (result.get() != null)                        return;                    addToPendingCount(1);                    new SearchEntriesTask<K,V,U>                        (this, batch >>>= 1, baseLimit = h, f, tab,                         searchFunction, result).fork();                }                while (result.get() == null) {                    U u;                    Node<K,V> p;                    if ((p = advance()) == null) {                        propagateCompletion();                        break;                    }                    if ((u = searchFunction.apply(p)) != null) {                        if (result.compareAndSet(null, u))                            quietlyCompleteRoot();                        return;                    }                }            }        }    }
    @SuppressWarnings("serial")    static final class SearchMappingsTask<K,V,U>        extends BulkTask<K,V,U> {        final BiFunction<? super K, ? super V, ? extends U> searchFunction;        final AtomicReference<U> result;        SearchMappingsTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             BiFunction<? super K, ? super V, ? extends U> searchFunction,             AtomicReference<U> result) {            super(p, b, i, f, t);            this.searchFunction = searchFunction; this.result = result;        }        public final U getRawResult() { return result.get(); }        public final void compute() {            final BiFunction<? super K, ? super V, ? extends U> searchFunction;            final AtomicReference<U> result;            if ((searchFunction = this.searchFunction) != null &&                (result = this.result) != null) {                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    if (result.get() != null)                        return;                    addToPendingCount(1);                    new SearchMappingsTask<K,V,U>                        (this, batch >>>= 1, baseLimit = h, f, tab,                         searchFunction, result).fork();                }                while (result.get() == null) {                    U u;                    Node<K,V> p;                    if ((p = advance()) == null) {                        propagateCompletion();                        break;                    }                    if ((u = searchFunction.apply(p.key, p.val)) != null) {                        if (result.compareAndSet(null, u))                            quietlyCompleteRoot();                        break;                    }                }            }        }    }
    @SuppressWarnings("serial")    static final class ReduceKeysTask<K,V>        extends BulkTask<K,V,K> {        final BiFunction<? super K, ? super K, ? extends K> reducer;        K result;        ReduceKeysTask<K,V> rights, nextRight;        ReduceKeysTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             ReduceKeysTask<K,V> nextRight,             BiFunction<? super K, ? super K, ? extends K> reducer) {            super(p, b, i, f, t); this.nextRight = nextRight;            this.reducer = reducer;        }        public final K getRawResult() { return result; }        public final void compute() {            final BiFunction<? super K, ? super K, ? extends K> reducer;            if ((reducer = this.reducer) != null) {                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    (rights = new ReduceKeysTask<K,V>                     (this, batch >>>= 1, baseLimit = h, f, tab,                      rights, reducer)).fork();                }                K r = null;                for (Node<K,V> p; (p = advance()) != null; ) {                    K u = p.key;                    r = (r == null) ? u : u == null ? r : reducer.apply(r, u);                }                result = r;                CountedCompleter<?> c;                for (c = firstComplete(); c != null; c = c.nextComplete()) {                    @SuppressWarnings("unchecked")                    ReduceKeysTask<K,V>                        t = (ReduceKeysTask<K,V>)c,                        s = t.rights;                    while (s != null) {                        K tr, sr;                        if ((sr = s.result) != null)                            t.result = (((tr = t.result) == null) ? sr :                                        reducer.apply(tr, sr));                        s = t.rights = s.nextRight;                    }                }            }        }    }
    @SuppressWarnings("serial")    static final class ReduceValuesTask<K,V>        extends BulkTask<K,V,V> {        final BiFunction<? super V, ? super V, ? extends V> reducer;        V result;        ReduceValuesTask<K,V> rights, nextRight;        ReduceValuesTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             ReduceValuesTask<K,V> nextRight,             BiFunction<? super V, ? super V, ? extends V> reducer) {            super(p, b, i, f, t); this.nextRight = nextRight;            this.reducer = reducer;        }        public final V getRawResult() { return result; }        public final void compute() {            final BiFunction<? super V, ? super V, ? extends V> reducer;            if ((reducer = this.reducer) != null) {                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    (rights = new ReduceValuesTask<K,V>                     (this, batch >>>= 1, baseLimit = h, f, tab,                      rights, reducer)).fork();                }                V r = null;                for (Node<K,V> p; (p = advance()) != null; ) {                    V v = p.val;                    r = (r == null) ? v : reducer.apply(r, v);                }                result = r;                CountedCompleter<?> c;                for (c = firstComplete(); c != null; c = c.nextComplete()) {                    @SuppressWarnings("unchecked")                    ReduceValuesTask<K,V>                        t = (ReduceValuesTask<K,V>)c,                        s = t.rights;                    while (s != null) {                        V tr, sr;                        if ((sr = s.result) != null)                            t.result = (((tr = t.result) == null) ? sr :                                        reducer.apply(tr, sr));                        s = t.rights = s.nextRight;                    }                }            }        }    }
    @SuppressWarnings("serial")    static final class ReduceEntriesTask<K,V>        extends BulkTask<K,V,Map.Entry<K,V>> {        final BiFunction<Map.Entry<K,V>, Map.Entry<K,V>, ? extends Map.Entry<K,V>> reducer;        Map.Entry<K,V> result;        ReduceEntriesTask<K,V> rights, nextRight;        ReduceEntriesTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             ReduceEntriesTask<K,V> nextRight,             BiFunction<Entry<K,V>, Map.Entry<K,V>, ? extends Map.Entry<K,V>> reducer) {            super(p, b, i, f, t); this.nextRight = nextRight;            this.reducer = reducer;        }        public final Map.Entry<K,V> getRawResult() { return result; }        public final void compute() {            final BiFunction<Map.Entry<K,V>, Map.Entry<K,V>, ? extends Map.Entry<K,V>> reducer;            if ((reducer = this.reducer) != null) {                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    (rights = new ReduceEntriesTask<K,V>                     (this, batch >>>= 1, baseLimit = h, f, tab,                      rights, reducer)).fork();                }                Map.Entry<K,V> r = null;                for (Node<K,V> p; (p = advance()) != null; )                    r = (r == null) ? p : reducer.apply(r, p);                result = r;                CountedCompleter<?> c;                for (c = firstComplete(); c != null; c = c.nextComplete()) {                    @SuppressWarnings("unchecked")                    ReduceEntriesTask<K,V>                        t = (ReduceEntriesTask<K,V>)c,                        s = t.rights;                    while (s != null) {                        Map.Entry<K,V> tr, sr;                        if ((sr = s.result) != null)                            t.result = (((tr = t.result) == null) ? sr :                                        reducer.apply(tr, sr));                        s = t.rights = s.nextRight;                    }                }            }        }    }
    @SuppressWarnings("serial")    static final class MapReduceKeysTask<K,V,U>        extends BulkTask<K,V,U> {        final Function<? super K, ? extends U> transformer;        final BiFunction<? super U, ? super U, ? extends U> reducer;        U result;        MapReduceKeysTask<K,V,U> rights, nextRight;        MapReduceKeysTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             MapReduceKeysTask<K,V,U> nextRight,             Function<? super K, ? extends U> transformer,             BiFunction<? super U, ? super U, ? extends U> reducer) {            super(p, b, i, f, t); this.nextRight = nextRight;            this.transformer = transformer;            this.reducer = reducer;        }        public final U getRawResult() { return result; }        public final void compute() {            final Function<? super K, ? extends U> transformer;            final BiFunction<? super U, ? super U, ? extends U> reducer;            if ((transformer = this.transformer) != null &&                (reducer = this.reducer) != null) {                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    (rights = new MapReduceKeysTask<K,V,U>                     (this, batch >>>= 1, baseLimit = h, f, tab,                      rights, transformer, reducer)).fork();                }                U r = null;                for (Node<K,V> p; (p = advance()) != null; ) {                    U u;                    if ((u = transformer.apply(p.key)) != null)                        r = (r == null) ? u : reducer.apply(r, u);                }                result = r;                CountedCompleter<?> c;                for (c = firstComplete(); c != null; c = c.nextComplete()) {                    @SuppressWarnings("unchecked")                    MapReduceKeysTask<K,V,U>                        t = (MapReduceKeysTask<K,V,U>)c,                        s = t.rights;                    while (s != null) {                        U tr, sr;                        if ((sr = s.result) != null)                            t.result = (((tr = t.result) == null) ? sr :                                        reducer.apply(tr, sr));                        s = t.rights = s.nextRight;                    }                }            }        }    }
    @SuppressWarnings("serial")    static final class MapReduceValuesTask<K,V,U>        extends BulkTask<K,V,U> {        final Function<? super V, ? extends U> transformer;        final BiFunction<? super U, ? super U, ? extends U> reducer;        U result;        MapReduceValuesTask<K,V,U> rights, nextRight;        MapReduceValuesTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             MapReduceValuesTask<K,V,U> nextRight,             Function<? super V, ? extends U> transformer,             BiFunction<? super U, ? super U, ? extends U> reducer) {            super(p, b, i, f, t); this.nextRight = nextRight;            this.transformer = transformer;            this.reducer = reducer;        }        public final U getRawResult() { return result; }        public final void compute() {            final Function<? super V, ? extends U> transformer;            final BiFunction<? super U, ? super U, ? extends U> reducer;            if ((transformer = this.transformer) != null &&                (reducer = this.reducer) != null) {                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    (rights = new MapReduceValuesTask<K,V,U>                     (this, batch >>>= 1, baseLimit = h, f, tab,                      rights, transformer, reducer)).fork();                }                U r = null;                for (Node<K,V> p; (p = advance()) != null; ) {                    U u;                    if ((u = transformer.apply(p.val)) != null)                        r = (r == null) ? u : reducer.apply(r, u);                }                result = r;                CountedCompleter<?> c;                for (c = firstComplete(); c != null; c = c.nextComplete()) {                    @SuppressWarnings("unchecked")                    MapReduceValuesTask<K,V,U>                        t = (MapReduceValuesTask<K,V,U>)c,                        s = t.rights;                    while (s != null) {                        U tr, sr;                        if ((sr = s.result) != null)                            t.result = (((tr = t.result) == null) ? sr :                                        reducer.apply(tr, sr));                        s = t.rights = s.nextRight;                    }                }            }        }    }
    @SuppressWarnings("serial")    static final class MapReduceEntriesTask<K,V,U>        extends BulkTask<K,V,U> {        final Function<Map.Entry<K,V>, ? extends U> transformer;        final BiFunction<? super U, ? super U, ? extends U> reducer;        U result;        MapReduceEntriesTask<K,V,U> rights, nextRight;        MapReduceEntriesTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             MapReduceEntriesTask<K,V,U> nextRight,             Function<Map.Entry<K,V>, ? extends U> transformer,             BiFunction<? super U, ? super U, ? extends U> reducer) {            super(p, b, i, f, t); this.nextRight = nextRight;            this.transformer = transformer;            this.reducer = reducer;        }        public final U getRawResult() { return result; }        public final void compute() {            final Function<Map.Entry<K,V>, ? extends U> transformer;            final BiFunction<? super U, ? super U, ? extends U> reducer;            if ((transformer = this.transformer) != null &&                (reducer = this.reducer) != null) {                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    (rights = new MapReduceEntriesTask<K,V,U>                     (this, batch >>>= 1, baseLimit = h, f, tab,                      rights, transformer, reducer)).fork();                }                U r = null;                for (Node<K,V> p; (p = advance()) != null; ) {                    U u;                    if ((u = transformer.apply(p)) != null)                        r = (r == null) ? u : reducer.apply(r, u);                }                result = r;                CountedCompleter<?> c;                for (c = firstComplete(); c != null; c = c.nextComplete()) {                    @SuppressWarnings("unchecked")                    MapReduceEntriesTask<K,V,U>                        t = (MapReduceEntriesTask<K,V,U>)c,                        s = t.rights;                    while (s != null) {                        U tr, sr;                        if ((sr = s.result) != null)                            t.result = (((tr = t.result) == null) ? sr :                                        reducer.apply(tr, sr));                        s = t.rights = s.nextRight;                    }                }            }        }    }
    @SuppressWarnings("serial")    static final class MapReduceMappingsTask<K,V,U>        extends BulkTask<K,V,U> {        final BiFunction<? super K, ? super V, ? extends U> transformer;        final BiFunction<? super U, ? super U, ? extends U> reducer;        U result;        MapReduceMappingsTask<K,V,U> rights, nextRight;        MapReduceMappingsTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             MapReduceMappingsTask<K,V,U> nextRight,             BiFunction<? super K, ? super V, ? extends U> transformer,             BiFunction<? super U, ? super U, ? extends U> reducer) {            super(p, b, i, f, t); this.nextRight = nextRight;            this.transformer = transformer;            this.reducer = reducer;        }        public final U getRawResult() { return result; }        public final void compute() {            final BiFunction<? super K, ? super V, ? extends U> transformer;            final BiFunction<? super U, ? super U, ? extends U> reducer;            if ((transformer = this.transformer) != null &&                (reducer = this.reducer) != null) {                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    (rights = new MapReduceMappingsTask<K,V,U>                     (this, batch >>>= 1, baseLimit = h, f, tab,                      rights, transformer, reducer)).fork();                }                U r = null;                for (Node<K,V> p; (p = advance()) != null; ) {                    U u;                    if ((u = transformer.apply(p.key, p.val)) != null)                        r = (r == null) ? u : reducer.apply(r, u);                }                result = r;                CountedCompleter<?> c;                for (c = firstComplete(); c != null; c = c.nextComplete()) {                    @SuppressWarnings("unchecked")                    MapReduceMappingsTask<K,V,U>                        t = (MapReduceMappingsTask<K,V,U>)c,                        s = t.rights;                    while (s != null) {                        U tr, sr;                        if ((sr = s.result) != null)                            t.result = (((tr = t.result) == null) ? sr :                                        reducer.apply(tr, sr));                        s = t.rights = s.nextRight;                    }                }            }        }    }
    @SuppressWarnings("serial")    static final class MapReduceKeysToDoubleTask<K,V>        extends BulkTask<K,V,Double> {        final ToDoubleFunction<? super K> transformer;        final DoubleBinaryOperator reducer;        final double basis;        double result;        MapReduceKeysToDoubleTask<K,V> rights, nextRight;        MapReduceKeysToDoubleTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             MapReduceKeysToDoubleTask<K,V> nextRight,             ToDoubleFunction<? super K> transformer,             double basis,             DoubleBinaryOperator reducer) {            super(p, b, i, f, t); this.nextRight = nextRight;            this.transformer = transformer;            this.basis = basis; this.reducer = reducer;        }        public final Double getRawResult() { return result; }        public final void compute() {            final ToDoubleFunction<? super K> transformer;            final DoubleBinaryOperator reducer;            if ((transformer = this.transformer) != null &&                (reducer = this.reducer) != null) {                double r = this.basis;                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    (rights = new MapReduceKeysToDoubleTask<K,V>                     (this, batch >>>= 1, baseLimit = h, f, tab,                      rights, transformer, r, reducer)).fork();                }                for (Node<K,V> p; (p = advance()) != null; )                    r = reducer.applyAsDouble(r, transformer.applyAsDouble(p.key));                result = r;                CountedCompleter<?> c;                for (c = firstComplete(); c != null; c = c.nextComplete()) {                    @SuppressWarnings("unchecked")                    MapReduceKeysToDoubleTask<K,V>                        t = (MapReduceKeysToDoubleTask<K,V>)c,                        s = t.rights;                    while (s != null) {                        t.result = reducer.applyAsDouble(t.result, s.result);                        s = t.rights = s.nextRight;                    }                }            }        }    }
    @SuppressWarnings("serial")    static final class MapReduceValuesToDoubleTask<K,V>        extends BulkTask<K,V,Double> {        final ToDoubleFunction<? super V> transformer;        final DoubleBinaryOperator reducer;        final double basis;        double result;        MapReduceValuesToDoubleTask<K,V> rights, nextRight;        MapReduceValuesToDoubleTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             MapReduceValuesToDoubleTask<K,V> nextRight,             ToDoubleFunction<? super V> transformer,             double basis,             DoubleBinaryOperator reducer) {            super(p, b, i, f, t); this.nextRight = nextRight;            this.transformer = transformer;            this.basis = basis; this.reducer = reducer;        }        public final Double getRawResult() { return result; }        public final void compute() {            final ToDoubleFunction<? super V> transformer;            final DoubleBinaryOperator reducer;            if ((transformer = this.transformer) != null &&                (reducer = this.reducer) != null) {                double r = this.basis;                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    (rights = new MapReduceValuesToDoubleTask<K,V>                     (this, batch >>>= 1, baseLimit = h, f, tab,                      rights, transformer, r, reducer)).fork();                }                for (Node<K,V> p; (p = advance()) != null; )                    r = reducer.applyAsDouble(r, transformer.applyAsDouble(p.val));                result = r;                CountedCompleter<?> c;                for (c = firstComplete(); c != null; c = c.nextComplete()) {                    @SuppressWarnings("unchecked")                    MapReduceValuesToDoubleTask<K,V>                        t = (MapReduceValuesToDoubleTask<K,V>)c,                        s = t.rights;                    while (s != null) {                        t.result = reducer.applyAsDouble(t.result, s.result);                        s = t.rights = s.nextRight;                    }                }            }        }    }
    @SuppressWarnings("serial")    static final class MapReduceEntriesToDoubleTask<K,V>        extends BulkTask<K,V,Double> {        final ToDoubleFunction<Map.Entry<K,V>> transformer;        final DoubleBinaryOperator reducer;        final double basis;        double result;        MapReduceEntriesToDoubleTask<K,V> rights, nextRight;        MapReduceEntriesToDoubleTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             MapReduceEntriesToDoubleTask<K,V> nextRight,             ToDoubleFunction<Map.Entry<K,V>> transformer,             double basis,             DoubleBinaryOperator reducer) {            super(p, b, i, f, t); this.nextRight = nextRight;            this.transformer = transformer;            this.basis = basis; this.reducer = reducer;        }        public final Double getRawResult() { return result; }        public final void compute() {            final ToDoubleFunction<Map.Entry<K,V>> transformer;            final DoubleBinaryOperator reducer;            if ((transformer = this.transformer) != null &&                (reducer = this.reducer) != null) {                double r = this.basis;                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    (rights = new MapReduceEntriesToDoubleTask<K,V>                     (this, batch >>>= 1, baseLimit = h, f, tab,                      rights, transformer, r, reducer)).fork();                }                for (Node<K,V> p; (p = advance()) != null; )                    r = reducer.applyAsDouble(r, transformer.applyAsDouble(p));                result = r;                CountedCompleter<?> c;                for (c = firstComplete(); c != null; c = c.nextComplete()) {                    @SuppressWarnings("unchecked")                    MapReduceEntriesToDoubleTask<K,V>                        t = (MapReduceEntriesToDoubleTask<K,V>)c,                        s = t.rights;                    while (s != null) {                        t.result = reducer.applyAsDouble(t.result, s.result);                        s = t.rights = s.nextRight;                    }                }            }        }    }
    @SuppressWarnings("serial")    static final class MapReduceMappingsToDoubleTask<K,V>        extends BulkTask<K,V,Double> {        final ToDoubleBiFunction<? super K, ? super V> transformer;        final DoubleBinaryOperator reducer;        final double basis;        double result;        MapReduceMappingsToDoubleTask<K,V> rights, nextRight;        MapReduceMappingsToDoubleTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             MapReduceMappingsToDoubleTask<K,V> nextRight,             ToDoubleBiFunction<? super K, ? super V> transformer,             double basis,             DoubleBinaryOperator reducer) {            super(p, b, i, f, t); this.nextRight = nextRight;            this.transformer = transformer;            this.basis = basis; this.reducer = reducer;        }        public final Double getRawResult() { return result; }        public final void compute() {            final ToDoubleBiFunction<? super K, ? super V> transformer;            final DoubleBinaryOperator reducer;            if ((transformer = this.transformer) != null &&                (reducer = this.reducer) != null) {                double r = this.basis;                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    (rights = new MapReduceMappingsToDoubleTask<K,V>                     (this, batch >>>= 1, baseLimit = h, f, tab,                      rights, transformer, r, reducer)).fork();                }                for (Node<K,V> p; (p = advance()) != null; )                    r = reducer.applyAsDouble(r, transformer.applyAsDouble(p.key, p.val));                result = r;                CountedCompleter<?> c;                for (c = firstComplete(); c != null; c = c.nextComplete()) {                    @SuppressWarnings("unchecked")                    MapReduceMappingsToDoubleTask<K,V>                        t = (MapReduceMappingsToDoubleTask<K,V>)c,                        s = t.rights;                    while (s != null) {                        t.result = reducer.applyAsDouble(t.result, s.result);                        s = t.rights = s.nextRight;                    }                }            }        }    }
    @SuppressWarnings("serial")    static final class MapReduceKeysToLongTask<K,V>        extends BulkTask<K,V,Long> {        final ToLongFunction<? super K> transformer;        final LongBinaryOperator reducer;        final long basis;        long result;        MapReduceKeysToLongTask<K,V> rights, nextRight;        MapReduceKeysToLongTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             MapReduceKeysToLongTask<K,V> nextRight,             ToLongFunction<? super K> transformer,             long basis,             LongBinaryOperator reducer) {            super(p, b, i, f, t); this.nextRight = nextRight;            this.transformer = transformer;            this.basis = basis; this.reducer = reducer;        }        public final Long getRawResult() { return result; }        public final void compute() {            final ToLongFunction<? super K> transformer;            final LongBinaryOperator reducer;            if ((transformer = this.transformer) != null &&                (reducer = this.reducer) != null) {                long r = this.basis;                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    (rights = new MapReduceKeysToLongTask<K,V>                     (this, batch >>>= 1, baseLimit = h, f, tab,                      rights, transformer, r, reducer)).fork();                }                for (Node<K,V> p; (p = advance()) != null; )                    r = reducer.applyAsLong(r, transformer.applyAsLong(p.key));                result = r;                CountedCompleter<?> c;                for (c = firstComplete(); c != null; c = c.nextComplete()) {                    @SuppressWarnings("unchecked")                    MapReduceKeysToLongTask<K,V>                        t = (MapReduceKeysToLongTask<K,V>)c,                        s = t.rights;                    while (s != null) {                        t.result = reducer.applyAsLong(t.result, s.result);                        s = t.rights = s.nextRight;                    }                }            }        }    }
    @SuppressWarnings("serial")    static final class MapReduceValuesToLongTask<K,V>        extends BulkTask<K,V,Long> {        final ToLongFunction<? super V> transformer;        final LongBinaryOperator reducer;        final long basis;        long result;        MapReduceValuesToLongTask<K,V> rights, nextRight;        MapReduceValuesToLongTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             MapReduceValuesToLongTask<K,V> nextRight,             ToLongFunction<? super V> transformer,             long basis,             LongBinaryOperator reducer) {            super(p, b, i, f, t); this.nextRight = nextRight;            this.transformer = transformer;            this.basis = basis; this.reducer = reducer;        }        public final Long getRawResult() { return result; }        public final void compute() {            final ToLongFunction<? super V> transformer;            final LongBinaryOperator reducer;            if ((transformer = this.transformer) != null &&                (reducer = this.reducer) != null) {                long r = this.basis;                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    (rights = new MapReduceValuesToLongTask<K,V>                     (this, batch >>>= 1, baseLimit = h, f, tab,                      rights, transformer, r, reducer)).fork();                }                for (Node<K,V> p; (p = advance()) != null; )                    r = reducer.applyAsLong(r, transformer.applyAsLong(p.val));                result = r;                CountedCompleter<?> c;                for (c = firstComplete(); c != null; c = c.nextComplete()) {                    @SuppressWarnings("unchecked")                    MapReduceValuesToLongTask<K,V>                        t = (MapReduceValuesToLongTask<K,V>)c,                        s = t.rights;                    while (s != null) {                        t.result = reducer.applyAsLong(t.result, s.result);                        s = t.rights = s.nextRight;                    }                }            }        }    }
    @SuppressWarnings("serial")    static final class MapReduceEntriesToLongTask<K,V>        extends BulkTask<K,V,Long> {        final ToLongFunction<Map.Entry<K,V>> transformer;        final LongBinaryOperator reducer;        final long basis;        long result;        MapReduceEntriesToLongTask<K,V> rights, nextRight;        MapReduceEntriesToLongTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             MapReduceEntriesToLongTask<K,V> nextRight,             ToLongFunction<Map.Entry<K,V>> transformer,             long basis,             LongBinaryOperator reducer) {            super(p, b, i, f, t); this.nextRight = nextRight;            this.transformer = transformer;            this.basis = basis; this.reducer = reducer;        }        public final Long getRawResult() { return result; }        public final void compute() {            final ToLongFunction<Map.Entry<K,V>> transformer;            final LongBinaryOperator reducer;            if ((transformer = this.transformer) != null &&                (reducer = this.reducer) != null) {                long r = this.basis;                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    (rights = new MapReduceEntriesToLongTask<K,V>                     (this, batch >>>= 1, baseLimit = h, f, tab,                      rights, transformer, r, reducer)).fork();                }                for (Node<K,V> p; (p = advance()) != null; )                    r = reducer.applyAsLong(r, transformer.applyAsLong(p));                result = r;                CountedCompleter<?> c;                for (c = firstComplete(); c != null; c = c.nextComplete()) {                    @SuppressWarnings("unchecked")                    MapReduceEntriesToLongTask<K,V>                        t = (MapReduceEntriesToLongTask<K,V>)c,                        s = t.rights;                    while (s != null) {                        t.result = reducer.applyAsLong(t.result, s.result);                        s = t.rights = s.nextRight;                    }                }            }        }    }
    @SuppressWarnings("serial")    static final class MapReduceMappingsToLongTask<K,V>        extends BulkTask<K,V,Long> {        final ToLongBiFunction<? super K, ? super V> transformer;        final LongBinaryOperator reducer;        final long basis;        long result;        MapReduceMappingsToLongTask<K,V> rights, nextRight;        MapReduceMappingsToLongTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             MapReduceMappingsToLongTask<K,V> nextRight,             ToLongBiFunction<? super K, ? super V> transformer,             long basis,             LongBinaryOperator reducer) {            super(p, b, i, f, t); this.nextRight = nextRight;            this.transformer = transformer;            this.basis = basis; this.reducer = reducer;        }        public final Long getRawResult() { return result; }        public final void compute() {            final ToLongBiFunction<? super K, ? super V> transformer;            final LongBinaryOperator reducer;            if ((transformer = this.transformer) != null &&                (reducer = this.reducer) != null) {                long r = this.basis;                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    (rights = new MapReduceMappingsToLongTask<K,V>                     (this, batch >>>= 1, baseLimit = h, f, tab,                      rights, transformer, r, reducer)).fork();                }                for (Node<K,V> p; (p = advance()) != null; )                    r = reducer.applyAsLong(r, transformer.applyAsLong(p.key, p.val));                result = r;                CountedCompleter<?> c;                for (c = firstComplete(); c != null; c = c.nextComplete()) {                    @SuppressWarnings("unchecked")                    MapReduceMappingsToLongTask<K,V>                        t = (MapReduceMappingsToLongTask<K,V>)c,                        s = t.rights;                    while (s != null) {                        t.result = reducer.applyAsLong(t.result, s.result);                        s = t.rights = s.nextRight;                    }                }            }        }    }
    @SuppressWarnings("serial")    static final class MapReduceKeysToIntTask<K,V>        extends BulkTask<K,V,Integer> {        final ToIntFunction<? super K> transformer;        final IntBinaryOperator reducer;        final int basis;        int result;        MapReduceKeysToIntTask<K,V> rights, nextRight;        MapReduceKeysToIntTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             MapReduceKeysToIntTask<K,V> nextRight,             ToIntFunction<? super K> transformer,             int basis,             IntBinaryOperator reducer) {            super(p, b, i, f, t); this.nextRight = nextRight;            this.transformer = transformer;            this.basis = basis; this.reducer = reducer;        }        public final Integer getRawResult() { return result; }        public final void compute() {            final ToIntFunction<? super K> transformer;            final IntBinaryOperator reducer;            if ((transformer = this.transformer) != null &&                (reducer = this.reducer) != null) {                int r = this.basis;                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    (rights = new MapReduceKeysToIntTask<K,V>                     (this, batch >>>= 1, baseLimit = h, f, tab,                      rights, transformer, r, reducer)).fork();                }                for (Node<K,V> p; (p = advance()) != null; )                    r = reducer.applyAsInt(r, transformer.applyAsInt(p.key));                result = r;                CountedCompleter<?> c;                for (c = firstComplete(); c != null; c = c.nextComplete()) {                    @SuppressWarnings("unchecked")                    MapReduceKeysToIntTask<K,V>                        t = (MapReduceKeysToIntTask<K,V>)c,                        s = t.rights;                    while (s != null) {                        t.result = reducer.applyAsInt(t.result, s.result);                        s = t.rights = s.nextRight;                    }                }            }        }    }
    @SuppressWarnings("serial")    static final class MapReduceValuesToIntTask<K,V>        extends BulkTask<K,V,Integer> {        final ToIntFunction<? super V> transformer;        final IntBinaryOperator reducer;        final int basis;        int result;        MapReduceValuesToIntTask<K,V> rights, nextRight;        MapReduceValuesToIntTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             MapReduceValuesToIntTask<K,V> nextRight,             ToIntFunction<? super V> transformer,             int basis,             IntBinaryOperator reducer) {            super(p, b, i, f, t); this.nextRight = nextRight;            this.transformer = transformer;            this.basis = basis; this.reducer = reducer;        }        public final Integer getRawResult() { return result; }        public final void compute() {            final ToIntFunction<? super V> transformer;            final IntBinaryOperator reducer;            if ((transformer = this.transformer) != null &&                (reducer = this.reducer) != null) {                int r = this.basis;                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    (rights = new MapReduceValuesToIntTask<K,V>                     (this, batch >>>= 1, baseLimit = h, f, tab,                      rights, transformer, r, reducer)).fork();                }                for (Node<K,V> p; (p = advance()) != null; )                    r = reducer.applyAsInt(r, transformer.applyAsInt(p.val));                result = r;                CountedCompleter<?> c;                for (c = firstComplete(); c != null; c = c.nextComplete()) {                    @SuppressWarnings("unchecked")                    MapReduceValuesToIntTask<K,V>                        t = (MapReduceValuesToIntTask<K,V>)c,                        s = t.rights;                    while (s != null) {                        t.result = reducer.applyAsInt(t.result, s.result);                        s = t.rights = s.nextRight;                    }                }            }        }    }
    @SuppressWarnings("serial")    static final class MapReduceEntriesToIntTask<K,V>        extends BulkTask<K,V,Integer> {        final ToIntFunction<Map.Entry<K,V>> transformer;        final IntBinaryOperator reducer;        final int basis;        int result;        MapReduceEntriesToIntTask<K,V> rights, nextRight;        MapReduceEntriesToIntTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             MapReduceEntriesToIntTask<K,V> nextRight,             ToIntFunction<Map.Entry<K,V>> transformer,             int basis,             IntBinaryOperator reducer) {            super(p, b, i, f, t); this.nextRight = nextRight;            this.transformer = transformer;            this.basis = basis; this.reducer = reducer;        }        public final Integer getRawResult() { return result; }        public final void compute() {            final ToIntFunction<Map.Entry<K,V>> transformer;            final IntBinaryOperator reducer;            if ((transformer = this.transformer) != null &&                (reducer = this.reducer) != null) {                int r = this.basis;                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    (rights = new MapReduceEntriesToIntTask<K,V>                     (this, batch >>>= 1, baseLimit = h, f, tab,                      rights, transformer, r, reducer)).fork();                }                for (Node<K,V> p; (p = advance()) != null; )                    r = reducer.applyAsInt(r, transformer.applyAsInt(p));                result = r;                CountedCompleter<?> c;                for (c = firstComplete(); c != null; c = c.nextComplete()) {                    @SuppressWarnings("unchecked")                    MapReduceEntriesToIntTask<K,V>                        t = (MapReduceEntriesToIntTask<K,V>)c,                        s = t.rights;                    while (s != null) {                        t.result = reducer.applyAsInt(t.result, s.result);                        s = t.rights = s.nextRight;                    }                }            }        }    }
    @SuppressWarnings("serial")    static final class MapReduceMappingsToIntTask<K,V>        extends BulkTask<K,V,Integer> {        final ToIntBiFunction<? super K, ? super V> transformer;        final IntBinaryOperator reducer;        final int basis;        int result;        MapReduceMappingsToIntTask<K,V> rights, nextRight;        MapReduceMappingsToIntTask            (BulkTask<K,V,?> p, int b, int i, int f, Node<K,V>[] t,             MapReduceMappingsToIntTask<K,V> nextRight,             ToIntBiFunction<? super K, ? super V> transformer,             int basis,             IntBinaryOperator reducer) {            super(p, b, i, f, t); this.nextRight = nextRight;            this.transformer = transformer;            this.basis = basis; this.reducer = reducer;        }        public final Integer getRawResult() { return result; }        public final void compute() {            final ToIntBiFunction<? super K, ? super V> transformer;            final IntBinaryOperator reducer;            if ((transformer = this.transformer) != null &&                (reducer = this.reducer) != null) {                int r = this.basis;                for (int i = baseIndex, f, h; batch > 0 &&                         (h = ((f = baseLimit) + i) >>> 1) > i;) {                    addToPendingCount(1);                    (rights = new MapReduceMappingsToIntTask<K,V>                     (this, batch >>>= 1, baseLimit = h, f, tab,                      rights, transformer, r, reducer)).fork();                }                for (Node<K,V> p; (p = advance()) != null; )                    r = reducer.applyAsInt(r, transformer.applyAsInt(p.key, p.val));                result = r;                CountedCompleter<?> c;                for (c = firstComplete(); c != null; c = c.nextComplete()) {                    @SuppressWarnings("unchecked")                    MapReduceMappingsToIntTask<K,V>                        t = (MapReduceMappingsToIntTask<K,V>)c,                        s = t.rights;                    while (s != null) {                        t.result = reducer.applyAsInt(t.result, s.result);                        s = t.rights = s.nextRight;                    }                }            }        }    }
    // Unsafe mechanics    private static final sun.misc.Unsafe U;    private static final long SIZECTL;    private static final long TRANSFERINDEX;    private static final long BASECOUNT;    private static final long CELLSBUSY;    private static final long CELLVALUE;    private static final long ABASE;    private static final int ASHIFT;
    static {        try {            U = sun.misc.Unsafe.getUnsafe();            Class<?> k = ConcurrentHashMap.class;            SIZECTL = U.objectFieldOffset                (k.getDeclaredField("sizeCtl"));            TRANSFERINDEX = U.objectFieldOffset                (k.getDeclaredField("transferIndex"));            BASECOUNT = U.objectFieldOffset                (k.getDeclaredField("baseCount"));            CELLSBUSY = U.objectFieldOffset                (k.getDeclaredField("cellsBusy"));            Class<?> ck = CounterCell.class;            CELLVALUE = U.objectFieldOffset                (ck.getDeclaredField("value"));            Class<?> ak = Node[].class;            ABASE = U.arrayBaseOffset(ak);            int scale = U.arrayIndexScale(ak);            if ((scale & (scale - 1)) != 0)                throw new Error("data type scale not a power of two");            ASHIFT = 31 - Integer.numberOfLeadingZeros(scale);        } catch (Exception e) {            throw new Error(e);        }    }}


原文链接:https://www.cnblogs.com/shuimutong/p/12128434.html
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