java并发编程CountDownLatch

/**
     * CountDownLatch用法
     * CountDownLatch类位于java.util.concurrent包下，利用它可以实现类似计数器的功能。比如有一个任务A，
     * 它要等待其他4个任务执行完毕之后才能执行，此时就可以利用CountDownLatch来实现这种功能了
     */
    @Test
    public void getThread(){
        final CountDownLatch latch = new CountDownLatch(2);
        new Thread (){
            @Override
            public void run() {
                try {
                    System.out.println("子线程"+Thread.currentThread().getName()+"正在执行");
                    Thread.sleep(3000);
                    System.out.println("子线程"+Thread.currentThread().getName()+"执行完毕");
                    latch.countDown();
                    System.out.println(latch);
                }catch (InterruptedException e){
                    e.printStackTrace();
                }
            }
        }.start();
        new Thread (){
            @Override
            public void run() {
                try {
                    System.out.println("子线程"+Thread.currentThread().getName()+"正在执行");
                    Thread.sleep(3000);
                    System.out.println("子线程"+Thread.currentThread().getName()+"执行完毕");
                    latch.countDown();
                    System.out.println(latch);
                }catch (InterruptedException e){
                    e.printStackTrace();
                }
            }
        }.start();

        try {
            System.out.println("等待2个子线程执行完毕...");
            latch.await();
            System.out.println("2个子线程已经执行完毕");
            System.out.println("继续执行主线程");
        }catch(InterruptedException e){
            e.printStackTrace();
        }
    }