Java并发编程之栅栏(CyclicBarrier)实例介绍

栅栏类似闭锁,但是它们是有区别的.

1.闭锁用来等待事件，而栅栏用于等待其他线程.什么意思呢?就是说闭锁用来等待的事件就是countDown事件,只有该countDown事件执行后所有之前在等待的线程才有可能继续执行;而栅栏没有类似countDown事件控制线程的执行,只有线程的await方法能控制等待的线程执行.

2.CyclicBarrier强调的是n个线程，大家相互等待，只要有一个没完成，所有人都得等着。

场景分析:10个人去春游,规定达到一个地点后才能继续前行.代码如下

import java.util.concurrent.BrokenBarrierException;

import java.util.concurrent.CyclicBarrier;

class CyclicBarrierWorker implements Runnable {

    private int id;

    private CyclicBarrier barrier;
    public CyclicBarrierWorker(int id, final CyclicBarrier barrier) {

        this.id = id;

        this.barrier = barrier;

    }
    @Override

    public void run() {

        // TODO Auto-generated method stub

        try {

            System.out.println(id + " th people wait");

            barrier.await(); // 大家等待最后一个线程到达

        } catch (InterruptedException | BrokenBarrierException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

    }

}
public class TestCyclicBarrier {

    public static void main(String[] args) {

        int num = 10;

        CyclicBarrier barrier = new CyclicBarrier(num, new Runnable() {

            @Override

            public void run() {

                // TODO Auto-generated method stub

                System.out.println("go on together!");

            }

        });

        for (int i = 1; i <= num; i++) {

            new Thread(new CyclicBarrierWorker(i, barrier)).start();

        }

    }

}

1 th people wait

2 th people wait

3 th people wait

4 th people wait

5 th people wait

7 th people wait

8 th people wait

6 th people wait

9 th people wait

10 th people wait

go on together!