CountDownLatch countDownLatch = new CountDownLatch(5);
        for (int i = 0; i < 5; i++) {
            final int index = i;
            new Thread(() -> {
                try {
                    Thread.sleep(30000 + ThreadLocalRandom.current().nextInt(1000));
                    System.out.println("finish" + index + Thread.currentThread().getName());
                    countDownLatch.countDown();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }).start();
        }
        System.out.println("主线程开始等待30秒");
        countDownLatch.await(10, TimeUnit.SECONDS);// 主线程在阻塞，当计数器==0或者等待超时，就唤醒主线程往下执行。
        System.out.println("主线程:在所有任务运行完成后，进行结果汇总");

CountDownLatch countDownLatch = new CountDownLatch(1);
        for (int i = 0; i < 5; i++) {
            new Thread(() -> {
                try {
                    //准备完毕……运动员都阻塞在这，等待号令
                    countDownLatch.await();
                    String parter = "【" + Thread.currentThread().getName() + "】";
                    System.out.println(parter + "开始执行……");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }).start();
        }

        Thread.sleep(2000);// 裁判准备发令
        System.out.println("准备执行");
        countDownLatch.countDown();// 发令枪：执行发令