Java中的共享锁CountDownLatch及源码解析

public class Test {
    public static void main(String[] args) throws InterruptedException {
        CountDownLatch latch = new CountDownLatch(3);
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    throw new RuntimeException(e);
                }
                System.out.println("线程一执行完成");
                latch.countDown();
            }
        }).start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    throw new RuntimeException(e);
                }
                System.out.println("线程二执行完成");
                latch.countDown();
            }
        }).start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("线程三执行完成");
                latch.countDown();
            }
        }).start();
        System.out.println("主线程等待");
        latch.await();
        System.out.println("主线程开始执行");
    }
}

  public void countDown() {
        sync.releaseShared(1);
    }

 public void await() throws InterruptedException {
        sync.acquireSharedInterruptibly(1);
    }