java并发（三十）闭锁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);
构造方法参数指定了计数的次数
public void countDown();
countDown方法，当前线程调用此方法，则计数减一
public void await() throws InterruptedException
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

示例代码

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.CountDownLatch;

/**
 * 
 * @author piaohailin
 * @date   2014-5-6
 */
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("piaohailin", 5000, latch);
        Worker worker2 = new Worker("chinaso", 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();
            }
        }
    }

}

参考资料
http://www.blogjava.net/xylz/archive/2010/07/09/325612.html