CountDownLatch 多線程demo

CountDownLatch，一個同步輔助類，在完成一組正在其他線程中執行的操作之前，它允許一個或多個線程一直等待。

主要方法

public CountDownLatch(int count);

public void countDown();

public void await() throws
InterruptedException

構造方法參數指定了計數的次數

countDown方法，當前線程調用此方法，則計數減一

awaint方法，調用此方法會一直阻塞當前線程，直到計時器的值為0

例子

Java代碼

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);//兩個工人的協作 
   
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，計數器減一 
    
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. } 

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);//兩個工人的協作    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，計數器減一    }        private void doWork(){    try {Thread.sleep(workTime);} catch (InterruptedException e) {e.printStackTrace();}    }    }         }

輸出：

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