CountDownLatch

public class CountDownLatchDemo {
    //任务1-6做完后，打印：任务完成。
    public static void main(String[] args) throws InterruptedException {
        CountDownLatch countDownLatch = new CountDownLatch(6);
        for (int i=1; i<=6; i++){
            new Thread(()->{
                System.out.println(Thread.currentThread().getName()+"任务完成..");
                countDownLatch.countDown();
            },String.valueOf(i)).start();//给线程命名
        }
        countDownLatch.await();
        System.out.println("任务完成");
    }
}

结果：

思路就是：把数值减少到0才会放行。