Java多线程——之一创建线程的四种方法

2018-10-19 06:29:44来源：博客园阅读 ()

1.实现Runnable接口，重载run()，无返回值

package thread;

public class ThreadRunnable implements Runnable {
    public void run() {
        for (int i = 0; i < 10; i++) {
            System.out.println(Thread.currentThread().getName() + ":" + i);
        }
    }
}


package thread;

public class ThreadMain {
    public static void main(String[] args) throws Exception {
        ThreadRunnable threadRunnable1 = new ThreadRunnable();
        ThreadRunnable threadRunnable2 = new ThreadRunnable();
        ThreadRunnable threadRunnable3 = new ThreadRunnable();
        ThreadRunnable threadRunnable4 = new ThreadRunnable();
        Thread thread1 = new Thread(threadRunnable1);
        Thread thread2 = new Thread(threadRunnable2);
        Thread thread3 = new Thread(threadRunnable3);
        Thread thread4 = new Thread(threadRunnable4);
        thread1.start();
        thread2.start();
        thread3.start();
        thread4.start();
    }
}

2.继承Thread类，复写run()

使用时通过调用Thread的start()（该方法是native），再调用创建线程的run()，不同线程的run方法里面的代码交替执行。

不足：由于java为单继承，若使用线程类已经有个父类，则不能使用该方式创建线程。

public class ThreadEx extends Thread {
    public void run() {
        for (int i = 0; i < 10; i++) {
            System.out.println(Thread.currentThread() + ":" + i);
        }
    }
}


public class ThreadMain {
    public static void main(String[] args)
    {
        ThreadEx threadEx = new ThreadEx();
        threadEx.start();
    }
}

3.实现Callable接口，通过FutureTask/Future来创建有返回值的Thread线程，通过Executor执行

补充：与实现Runnable接口类似，都是实现接口，不同的是该方式有返回值，可以获得异步执行的结果。

延伸：FutureTask是类，Future是接口。

package thread;

import java.util.concurrent.*;

public class ThreadCallable {
    public static void main(String[] args) throws Exception {
        FutureTask<Integer> futureTask = new FutureTask<Integer>(new Callable<Integer>() {
            public Integer call() throws Exception {
                for (int i = 0; i < 10; i++) {
                    System.out.println(Thread.currentThread().getName() + ":" + i);
                }
                return 1;
            }
        });
        Executor executor = Executors.newFixedThreadPool(1);
        ((ExecutorService) executor).submit(futureTask);

        //获得线程执行状态
        System.out.println(Thread.currentThread().getName() + ":" + futureTask.get());
    }
}

4.使用Executors创建ExecutorService，入参Callable或Future

补充：适用于线程池和并发

package thread;

import java.util.concurrent.Callable;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;

import static java.lang.Thread.sleep;

public class ThreadExecutors {
    private final String threadName;

    public ThreadExecutors(String threadName) {
        this.threadName = threadName;
    }

    private ThreadFactory createThread() {
        ThreadFactory tf = new ThreadFactory() {
            public Thread newThread(Runnable r) {
                Thread thread = new Thread();
                thread.setName(threadName);
                thread.setDaemon(true);
                try {
                    sleep(1000);
                }
                catch (InterruptedException e) {
                    e.printStackTrace();
                }
                return thread;
            }
        };
        return tf;
    }

    public Object runCallable(Callable callable) {
        return Executors.newSingleThreadExecutor(createThread()).submit(callable);
    }

    public Object runFunture(Runnable runnable) {
        return Executors.newSingleThreadExecutor(createThread()).submit(runnable);
    }
}



package thread;

import java.util.concurrent.*;

public class ThreadMain {
    public static void main(String[] args) throws Exception {
        ThreadExecutors threadExecutors = new ThreadExecutors("callableThread");
        threadExecutors.runCallable(new Callable() {
            public String call() throws Exception {
                return "success";
            }
        });

        threadExecutors.runFunture(new Runnable() {
            public void run() {
                System.out.println("execute runnable thread.");
            }
        });
    }
}

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