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
例子
- 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();
- }
- }
- }
- }
输出：
Worker zhang san do work begin at 2011-04-14 11:05:11
Worker li si do work begin at 2011-04-14 11:05:11
Worker zhang san do work complete at 2011-04-14 11:05:16
Worker li si do work complete at 2011-04-14 11:05:19
all work done at 2011-04-14 11:05:19