作用:执行第一个参数指定的次数之后，最后一个线程执行第二个参数中的任务。

应用场景：在微服务中调用五个接口，确保5个接口执行完毕，再执行自己的业务逻辑。

import java.util.Random;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class CyclicBarrierDemo {

    static class Task implements Runnable {
        
        CyclicBarrier barrier;
        
        public Task(CyclicBarrier barrier) {
            this.barrier = barrier;
        }
        
        @Override
        public void run() {
            try {
                Thread.sleep(new Random().nextInt(10) * 1000);
                System.out.println(Thread.currentThread().getName() + " 检查火箭");
                barrier.await();//标记子任务执行完了,让count++  => 满足count => 调用CyclicBarrier的参数2任务

            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
    
    public static void main(String[] args) {
        int count = 10;
        ExecutorService exec = Executors.newFixedThreadPool(count);


        CyclicBarrier barrier = new CyclicBarrier(5, new Runnable() {
            
            @Override
            public void run() {
                System.out.println(Thread.currentThread().getName() + " -------------------发射火箭");
            }
        });
        
        for(int i = 0; i < count; i++) {
            exec.execute(new Task(barrier));
        }
        exec.shutdown();
    }
    
}