[译]Java Thread join示例与详解

Java Thread join示例与详解

Java Thread join方法用来暂停当前线程直到join操作上的线程结束。java中有三个重载的join方法：

public final void join()：此方法会把当前线程变为wait，直到执行join操作的线程结束，如果该线程在执行中被中断，则会抛出InterruptedException。

public final synchronized void join(long millis)：此方法会把当前线程变为wait，直到执行join操作的线程结束或者在执行join后等待millis的时间。因为线程调度依赖于操作系统的实现，因为这并不能保证当前线程一定会在millis时间变为RUnnable。

public final synchroinzed void join(long millis, int nanos)：此方法会把当前线程变为wait，直到执行join操作的线程结束或者在join后等待millis+nanos的时间。

下面的示例程序展示了Thread join方法的用法。在这段程序要保证main线程是最后一个完成的线程，同时保证第三个线程(third thread)在第一个线程(first thread)结束后才开始执行。

package com.journaldev.threads;



public class ThreadJoinExample {



    public static void main(String[] args) {

        Thread t1 = new Thread(new MyRunnable(), "t1");

        Thread t2 = new Thread(new MyRunnable(), "t2");

        Thread t3 = new Thread(new MyRunnable(), "t3");



        t1.start();



        //start second thread after waiting for 2 seconds or if it's dead

        try {

            t1.join(2000);

        } catch (InterruptedException e) {

            e.printStackTrace();

        }



        t2.start();



        //start third thread only when first thread is dead

        try {

            t1.join();

        } catch (InterruptedException e) {

            e.printStackTrace();

        }



        t3.start();



        //let all threads finish execution before finishing main thread

        try {

            t1.join();

            t2.join();

            t3.join();

        } catch (InterruptedException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }



        System.out.println("All threads are dead, exiting main thread");

    }

}

 

class MyRunnable implements Runnable{



    @Override

    public void run() {

        System.out.println("Thread started:::"+Thread.currentThread().getName());

        try {

            Thread.sleep(4000);

        } catch (InterruptedException e) {

            e.printStackTrace();

        }

        System.out.println("Thread ended:::"+Thread.currentThread().getName());

    }  

}

 

程序输出结果如下：

Thread started:::t1
Thread ended:::t1
Thread started:::t2
Thread started:::t3
Thread ended:::t2
Thread ended:::t3
All threads are dead, exiting main thread

 

原文链接：http://www.journaldev.com/1024/java-thread-join-example-with-explanation