public class CountDownLatchExample1 {

    private static int threadCount = 10;

    public static void main(String[] args) throws InterruptedException {
        ExecutorService es = Executors.newCachedThreadPool();
        CountDownLatch countDownLatch = new CountDownLatch(threadCount);
        for (int i = 0; i < threadCount; i++) {
            final int count = i;
            es.execute(() -> {
                try {
                    test(count);
                } catch (Exception e) {
                    log.error("Exception,{}", e);
                } finally {
                    countDownLatch.countDown();
                }
            });
        }
        countDownLatch.await(1, TimeUnit.MILLISECONDS);
        log.info("======");
        es.shutdown();
    }

    public static void test(int i) throws InterruptedException {
        Thread.sleep(1000);//此方法延迟1秒再执行
        log.info("test {}", i);
    }

}

由于在方法里面加了一秒延迟 所以先打印出======,那为什么其他10条log信息同一秒出现了?