基于CyclicBarrier和CountDownLatch的使用区别说明

public static void main(String[] args) {
  ExecutorService pool = Executors.newCachedThreadPool();
  int size = 3;
  // 设置参数时，线程实际执行数size+1，将main线程也加到等待队列中
  CyclicBarrier cyclicBarrier = new CyclicBarrier(size + 1);
  for (int i = 0; i < size; i++) {
   int index = i;
   pool.submit(() -> {
    try {
     TimeUnit.SECONDS.sleep(index);
     System.out.println("第" + index + "位运动员准备好了");
     cyclicBarrier.await();
    } catch (Exception e) {
     e.printStackTrace();
    }
   });
  }
  try {
  //主线程也加入等待
   cyclicBarrier.await();
  } catch (Exception e) {
   e.printStackTrace();
  }
  System.out.println(size + "位运动员都准备好了，可以起跑!");
 }

import java.util.concurrent.*;

public class RunTest {
 public static void main(String[] args) {
  ExecutorService pool = Executors.newCachedThreadPool();
  int size = 3;
  CyclicBarrier cyclicBarrier = new CyclicBarrier(size, () -> {
   System.out.println(size + "位运动员都准备好了，可以起跑！");
   pool.shutdownNow();
  });

  for (int i = 0; i < size; i++) {
   int index = i;
   pool.submit(() -> {
    try {
     TimeUnit.SECONDS.sleep(index);
    } catch (InterruptedException e) {
     e.printStackTrace();
    }
    System.out.println("第" + index + "位运动员准备好了");
    try {
     cyclicBarrier.await();
    } catch (InterruptedException | BrokenBarrierException e) {
     e.printStackTrace();
    }
   });
  }
 }
}

import java.util.concurrent.*;

public class RunTest {
 public static void main(String[] args) throws InterruptedException {
  ExecutorService pool = Executors.newCachedThreadPool();
  CountDownLatch countDownLatch = new CountDownLatch(3);
  int size = 3;

  for (int i = 0; i < size; i++) {
   int index = i;
   pool.submit(() -> {
    try {
     TimeUnit.SECONDS.sleep(index);
     countDownLatch.countDown();
    } catch (InterruptedException e) {
     e.printStackTrace();
    }
    System.out.println("第" + index + "位运动员准备好了");
   });
  }
  countDownLatch.await();
  System.out.println(size + "位运动员都准备好了，可以起跑!");
 }
}