多线程CountDownLatch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() 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();              }          }      }               }  

转自：http://www.iteye.com/topic/1002652