CountDownLatchDemo about java-concurrency

[Buywatermelon]

发现这已经是一个2019年的Issue了，想必提问者随着阅历的增加早已找到了答案。而我作为一个正在学习的萌新在2021年看到了这个问题，便尝试着来解答一下。希望对未来的萌新有所帮助

• 我写了一段至少打印顺序正确的demo

    public void testCountDownLatch() throws InterruptedException {
        CountDownLatch judgeLatch = new CountDownLatch(1);
        CountDownLatch sportLatch = new CountDownLatch(8);
        CountDownLatch sportWaitLatch = new CountDownLatch(8);

        ExecutorService executorService = Executors.newFixedThreadPool(8);
        for (int i = 0; i < 8; i++) {
            executorService.execute(() -> {
                try {
                    log.info(Thread.currentThread().getName() + "运动员等待裁判员响哨！！！");
                    sportWaitLatch.countDown();

                    judgeLatch.await();
                    log.info(Thread.currentThread().getName() + "正在全力冲刺！！！");
                    log.info(Thread.currentThread().getName() + "到达终点");
                    sportLatch.countDown();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            });
        }

        sportWaitLatch.await();
        log.info("裁判员发号施令啦！！！");
        judgeLatch.countDown();

        sportLatch.await();
        log.info("所有运动员到达终点，比赛结束");
    }

• 可以看出区别在于打印“裁判员发号施令啦！！！”语句时，我用一个新的CountDownLatch对象await住了其他线程。
• 那么很容易就知道原本代码的问题在于：主线程在执行打印“裁判员发号施令啦！！！”时，线程池的遍历执行还没有集中执行到await()处。