CountDownLatch的用法

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() 

举例：

import java.text.SimpleDateFormat;import java.util.Date;import java.util.concurrent.CountDownLatch;public class CountDownLatchTest {private 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("bao", 2000, latch);          Worker worker2=new Worker("senan", 4000, latch);          worker1.start();          worker2.start();         latch.await();//等待所有worker完成工作          System.out.println("all work done at "+sdf.format(new Date()));  }static class Worker extends Thread{private String workerName;private int workTime;private 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(workerName + " start at" + sdf.format(new Date()));try {Thread.sleep(workTime);} catch (InterruptedException e) {e.printStackTrace();}finally{latch.countDown();//计数器减一}System.out.println(workerName + " end at" + sdf.format(new Date()));}}}