CountDownLatch和CyclicBarrier

CountDownLatch的基本使用

public static void main(String[] args) {
    CountDownLatch countDownLatch = new CountDownLatch(3);
    IntStream.range(0, 3).forEach(i -> new Thread(() -> {
        try {
            Thread.sleep(2000);
            System.out.println("hello");
        } catch (InterruptedException ex) {
            ex.printStackTrace();
        } finally {
            countDownLatch.countDown();
        }
    }).start());
    System.out.println("启动子线程完毕");
    try {
        countDownLatch.await();
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    System.out.println("主线程执行完毕");
}

CyclicBarrierd的基本使用

  public static void main(String[] args) {
      CyclicBarrier cyclicBarrier = new CyclicBarrier(3, () -> {
          System.out.println("hello world");
      });
      for (int i = 0; i < 2; ++i) {
          for (int n = 0; n < 3; ++n) {
              new Thread(() -> {
                  try {
                      Thread.sleep((long) (Math.random() * 2000));
                      int randomInt = new Random().nextInt(500);
                      System.out.println("hello " + randomInt);
                      cyclicBarrier.await();
                      System.out.println("world " + randomInt);
                  } catch (Exception ex) {
                      ex.printStackTrace();
                  }
              }).start();
          }
      }
  }