CountDownLatch countDownLatch = new CountDownLatch(5);
for (int i = 0; i < 5; i++) {
    new Thread(() -> {
        String name = Thread.currentThread().getName();
        System.out.println(name + "等待5秒" + LocalDateTime.now());
        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
        System.out.println(name + "扣減1" + LocalDateTime.now());
        countDownLatch.countDown();
    }).start();
}
try {
    countDownLatch.await();
} catch (InterruptedException e) {
    throw new RuntimeException(e);
}
System.out.println("finish");

CountDownLatch countDownLatch = new CountDownLatch(1);
for (int i = 0; i < 5; i++) {
       new Thread(() -> {
           String name = Thread.currentThread().getName();
           try {
               System.out.println(name + "準(zhǔn)備" + LocalDateTime.now());
               countDownLatch.await();
               System.out.println(name + "完成" + LocalDateTime.now());
           } catch (InterruptedException e) {
               throw new RuntimeException(e);
           }
       }).start();
}
try {
    Thread.sleep(5000);
    System.out.println("link start");
} catch (InterruptedException e) {
    throw new RuntimeException(e);
}
countDownLatch.countDown();