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CountDownLatch

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

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

 

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

CountDownLatch