JVM学习分享-练习题

2019-09-23 08:48:22来源:博客园 阅读 ()

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JVM学习分享-练习题

package org.fenixsoft.clazz;

public class TestClass {
private int m;

public int inc() {
return m + 1;
}
}


//----------- javap -verbose TestClass


package zero.desk.metaspace;

import org.springframework.cglib.proxy.Enhancer;
import org.springframework.cglib.proxy.MethodInterceptor;

/**
* @author:Zero
* @Description:
* @since 2019/6/11.
* 练习1
* VM Options:-XX:MetaspaceSize=10M -XX:MaxMetaspaceSize=10M
*/
public class MetaspaceOutmemory {
public static void main(String[] args) {
try {
System.out.println("MetaspaceOOM.java");
while (true) {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(OOMObject.class);
enhancer.setUseCache(false);
enhancer.setCallback(
(MethodInterceptor) (obj, method, args1, methodProxy) -> methodProxy.invokeSuper(obj, args1)
);
enhancer.create();
}
} catch (Exception e) {
e.printStackTrace();
}
}

static class OOMObject {
}
}

//------------------
package zero.desk.metaspace;

import java.util.ArrayList;
import java.util.List;

/**
* @author:Zero
* @Description:
* @since 2019/6/11.
* 练习2
* VM Options:-Xmx1M -Xms1M
*/
public class StringOutmemory {
static String base = "string";

public static void main(String[] args) {
try {
Thread.sleep(1000);
List<String> list = new ArrayList<String>();
for (int i = 0; i < Integer.MAX_VALUE; i++) {
String str = base + base;
base = str;
list.add(str.intern());
}
}catch (Exception e) {
e.printStackTrace();
}

}
}

//-------------
package zero.desk.gc;

/**
* @author Zero
* @since 2019-09-08.
* Description:使用默认垃圾收集器,Parallel Scavenge + Parallel Old
* 练习3
* VM Options:-XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps -XX:+PrintGCDetails
*/
public class ReferenceCountingGC {
public Object instance = null;
private static final int ONE_MB = 1024 * 1024;

private byte[] bigSize = new byte[2 * ONE_MB];

public static void main(String[] args) throws InterruptedException {
Thread.sleep(1000);
testGC();
Thread.sleep(1000);
}

public static void testGC() {
ReferenceCountingGC objA = new ReferenceCountingGC();
ReferenceCountingGC objB = new ReferenceCountingGC();
objA.instance = objB;
objB.instance = objA;

objA = null;
objB = null;

System.gc();
}
}

//-------------
package zero.desk.gc;

/**
* @author Zero
* @since 2019-09-08.
* Description:使用CMS收集器,ParNew + CMS
* 练习4
* VM Options:-XX:+UseConcMarkSweepGC -XX:+UseParNewGC -XX:+CMSParallelRemarkEnabled -XX:+UseCMSCompactAtFullCollection -XX:+PrintClassHistogram -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintHeapAtGC
*/
public class ReferenceCountingGCOpen {
public Object instance = null;
private static final int ONE_MB = 1024 * 1024;

private byte[] bigSize = new byte[2 * ONE_MB];

public static void main(String[] args) throws InterruptedException {
Thread.sleep(2000);
testGC();
Thread.sleep(1000);
}

public static void testGC() {
ReferenceCountingGCOpen objA = new ReferenceCountingGCOpen();
ReferenceCountingGCOpen objB = new ReferenceCountingGCOpen();
objA.instance = objB;
objB.instance = objA;

objA = null;
objB = null;

System.gc();
}
}

//--------------
package zero.desk.constantpool;

/**
* @author Zero
* @since 2019-09-08.
* Description:
* 练习5
* javap -verbose ConstantPool
*/
public class ConstantPool extends C implements A,B{
private String str = "test string";
private final int a = 10;
private final long b = 10;
private final long bb = 100;
private int c = 11;
private float d = 12f;
private float e = 12f;
private double ee = 12f;

private int m;

public int inc() {
return m + 1;
}
}

原文链接:https://www.cnblogs.com/DeskZero/p/11537520.html
如有疑问请与原作者联系

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