Java中类似C#中Task.wait()的类CountDownLatch

public static void main(String[] args) throws InterruptedException {        
    CountDownLatch latch = new CountDownLatch(3);
    for (int i = 0; i < 3; i++) {
        Thread t = new Thread() {
            public void run() {
                try {
                    Thread.sleep(2000);//暂停2秒
                    System.out.println("线程:"+this.getId()+"完成");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                latch.countDown();
            }
        };
        t.start();
    }
            
    System.out.println("等待3个线程完成");
    latch.await();//线程挂起，等待3个线程都执行完后再执行下面的内容
    System.out.println("3个线程都已完成");
}