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主线程等待一切子线程完成后再执行

编程语言 dzh213 55℃ 0评论
public class WaitThread {
    public static Lock lock = new ReentrantLock();

    public static void main(String[] args) throws InterruptedException {
        long time1 = System.currentTimeMillis();
        CountDownLatch countDownLatch = new CountDownLatch(10);
        for (int i = 0;i<10;i++){
            Thread thread = new Thread(new MyThread(countDownLatch));
            thread.start();
        }
        countDownLatch.await();//等待所有子线程执行完
        long time2 = System.currentTimeMillis();
        System.out.println("花费时间:"+(time2-time1));
        System.out.println(Thread.currentThread().getName() + "结束.");//打印结束标记
    }
}

class MyThread implements Runnable{

    private CountDownLatch countDownLatch;
    public MyThread(){}
    public MyThread(CountDownLatch countDownLatch){
        this.countDownLatch = countDownLatch;
    }

    @Override
    public void run() {
        WaitThread.lock.lock();
        try {
            System.out.println(Thread.currentThread().getName() + "开始...");
            //Do somethings
            countDownLatch.countDown();//线程结束时计数器减1
            System.out.println(Thread.currentThread().getName() + "结束. 还有" + countDownLatch.getCount() + " 个线程");
        }finally {
            WaitThread.lock.unlock();
        }
    }
}

执行结果:


Thread-0开始…


Thread-0结束. 还有9 个线程


Thread-7开始…


Thread-7结束. 还有8 个线程


Thread-1开始…


Thread-1结束. 还有7 个线程


Thread-2开始…


Thread-2结束. 还有6 个线程


Thread-3开始…


Thread-3结束. 还有5 个线程


Thread-4开始…


Thread-4结束. 还有4 个线程


Thread-5开始…


Thread-5结束. 还有3 个线程


Thread-6开始…


Thread-6结束. 还有2 个线程


Thread-8开始…


Thread-8结束. 还有1 个线程


Thread-9开始…


Thread-9结束. 还有0 个线程


花费时间:6


main结束.

public class WaitThread {
    public static Lock lock = new ReentrantLock();

    public static void main(String[] args) throws InterruptedException {
        ExecutorService exe = Executors.newFixedThreadPool(10);
        long time1 = System.currentTimeMillis();
        for (int i = 1; i <= 10; i++) {
            exe.execute(new MyThread());
        }
        exe.shutdown();//关闭线程池,不会真的关闭,只是不接收新任务
        while (true) {
            //判断是否所有线程都执行完毕
            if (exe.isTerminated()) {
                System.out.println("结束了!");
                long time2 = System.currentTimeMillis();
                System.out.println("花费时间:"+(time2-time1));
                break;
            }
            Thread.sleep(20);//防止循环很多次
        }
    }
}

class MyThread implements Runnable{

    @Override
    public void run() {
        WaitThread.lock.lock();
        try {
            System.out.println(Thread.currentThread().getName() + "开始...");

            System.out.println(Thread.currentThread().getName() + "结束.");
        }finally {
            WaitThread.lock.unlock();
        }
    }
}

执行结果:


pool-1-thread-1开始…


pool-1-thread-1结束.


pool-1-thread-2开始…


pool-1-thread-2结束.


pool-1-thread-4开始…


pool-1-thread-4结束.


pool-1-thread-3开始…


pool-1-thread-3结束.


pool-1-thread-5开始…


pool-1-thread-5结束.


pool-1-thread-6开始…


pool-1-thread-6结束.


pool-1-thread-7开始…


pool-1-thread-7结束.


pool-1-thread-10开始…


pool-1-thread-10结束.


pool-1-thread-9开始…


pool-1-thread-9结束.


pool-1-thread-8开始…


pool-1-thread-8结束.


结束了!


花费时间:23

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