Java之CountDownLatch使用

发表于 | 分类于 ，

1、CountDownLatch，一个同步辅助类，在完成一组正在其他线程中执行的操作之前，它允许一个或多个线程一直等待。
主要方法
public CountDownLatch(int count);
public void countDown();
public void await() throws InterruptedException

构造方法参数指定了计数的次数
countDown方法，当前线程调用此方法，则计数减一
awaint方法，调用此方法会一直阻塞当前线程，直到计时器的值为0

2、使用例子

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
package com.iseach.jdk.base.thread;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.CountDownLatch;
public class CountDownLatchDemo {
	final static SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
	public static void main(String[] args) throws InterruptedException {
		CountDownLatch latch = new CountDownLatch(2);// 两个工人的协作
		Worker worker1 = new Worker("zhang san", 5000, latch);
		Worker worker2 = new Worker("li si", 8000, latch);
		worker1.start();//
		worker2.start();//
		latch.await();// 等待所有工人完成工作
		System.out.println("all work done at " + sdf.format(new Date()));
	}
	static class Worker extends Thread {
		String workerName;
		int workTime;
		CountDownLatch latch;
		public Worker(String workerName, int workTime, CountDownLatch latch) {
			this.workerName = workerName;
			this.workTime = workTime;
			this.latch = latch;
		}
		public void run() {
			System.out.println("Worker " + workerName + " do work begin at " + sdf.format(new Date()));
			doWork();// 工作了
			System.out.println("Worker " + workerName + " do work complete at " + sdf.format(new Date()));
			latch.countDown();// 工人完成工作，计数器减一
		}
		private void doWork() {
			try {
				Thread.sleep(workTime);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
	}
}