java 多线程 CountDownLatch用法

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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

package com.dashu.demo;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);// 两个人协同工作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;}@Overridepublic void run() {// TODO Auto-generated method stubtry {System.out.println("Worker " + workerName+ " do work begin at " + sdf.format(new Date()));Thread.sleep(workTime);System.out.println("Worker " + workerName+ " do work complete at " + sdf.format(new Date()));} catch (Exception e) {// TODO: handle exception} finally {latch.countDown();// 工人完成工作，计数器减一}}}}

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