CountDownLatch

http://www.iteye.com/topic/1002652

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