CyclicBarrier

CyclicBarrier：多个线程同时工作以完成同一件事情，但在完成过程中，往往会等待其他线程都完成某一阶段后再执行，等所有线程都到达某一个阶段后再统一执行。CyclicBarrier最重要的属性就是参与者个数，另外最要方法是await()。当所有线程都调用了await()后，就表示这些线程都可以继续执行，否则就会等待。

package com.jerry.concurrency;

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

public class TestCyclicBarrier {
	
	 public static void main(String[] args) throws Exception{
		    // 4个年级
		    final CyclicBarrier barrier = new CyclicBarrier(4);
		    ExecutorService exec = Executors.newFixedThreadPool(4);
		    exec.submit(new Runnable() {
				@Override
				public void run() {
						try {
							Thread.sleep(5 * 1000);//一年级上5节课后放学
							System.out.println("一年级上完5节课了");
							barrier.await();
							Thread.sleep(6 * 1000);//一年级放学走了
							System.out.println("一年级放学走了");
							barrier.await();
						} catch (InterruptedException e) {
							e.printStackTrace();
						} catch (BrokenBarrierException e) {
							e.printStackTrace();
						}
				}
			});
		    exec.submit(new Runnable() {
				@Override
				public void run() {
						try {
							Thread.sleep(4 * 1000);//二年级上4节课后放学
							System.out.println("二年级上完4节课了");
							barrier.await();
							Thread.sleep(3 * 1000);//二年级放学走了
							System.out.println("二年级放学走了");
							barrier.await();
						} catch (InterruptedException e) {
							e.printStackTrace();
						} catch (BrokenBarrierException e) {
							e.printStackTrace();
						}
				}
			});
		    exec.submit(new Runnable() {
				@Override
				public void run() {
						try {
							Thread.sleep(6* 1000);//三年级上5节课后放学
							System.out.println("三年级上6节课了");
							barrier.await();
							Thread.sleep(6 * 1000);
							System.out.println("三年级放学走了");
							barrier.await();
						} catch (InterruptedException e) {
							e.printStackTrace();
						} catch (BrokenBarrierException e) {
							e.printStackTrace();
						}
				}
			});
		    exec.submit(new Runnable() {
				@Override
				public void run() {
						try {
							Thread.sleep(1 * 1000);//四年级上10节课后放学
							System.out.println("四年级上完1节课了");
							barrier.await();
							Thread.sleep(7 * 1000);
							System.out.println("四年级放学走了");
							barrier.await();
						} catch (InterruptedException e) {
							e.printStackTrace();
						} catch (BrokenBarrierException e) {
							e.printStackTrace();
						}
				}
			});
		    exec.shutdown();
		  }

}