import java.util.Random;
import java.util.concurrent.*;

/**
 * Created by Administrator on 2017/5/22 0022.
 */
public class Test {

    public static void main(String[] args) {
        //如果将参数改为4，但是下面只加入了3个选手，这永远等待下去
        CyclicBarrier barrier = new CyclicBarrier(3);
        ExecutorService executor = Executors.newFixedThreadPool(3);
        executor.submit(new Thread(new Runner(barrier,"1号选手")));
        executor.submit(new Thread(new Runner(barrier,"2号选手")));
        executor.submit(new Thread(new Runner(barrier,"3号选手")));
        executor.shutdown();

    }
}

class Runner implements Runnable{
    // 一个同步辅助类，它允许一组线程互相等待，直到到达某个公共屏障点 (common barrier point)
    private CyclicBarrier barrier;

    private String name;

    public Runner(CyclicBarrier barrier, String name) {
        super();
        this.barrier = barrier;
        this.name = name;
    }

    @Override
    public void run() {
        try {
            Thread.sleep(1000*(new Random()).nextInt(8));
            System.out.println(name+"准备好了！");
            barrier.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (BrokenBarrierException e) {
            e.printStackTrace();
        }

        System.out.println(name + " 起跑！");
    }

}