CountDownLatch 实例

   多线程模拟记者发布会。每个记者提一个问题，且发布会要等每个记者问题准备好，会议才能开始，待所有记者发问完后，会议结束。
   下面是模拟实例：

package cn.com.ld.study.thread;

/**   
 * @filename: Reporter   
 * @description: 记者  
 * @author lida  
 * @date 2013-3-29 下午1:35:01      
 */
public class Reporter {
	private String name;
	private String question;

	Reporter(String name, String question) {
		this.name = name;
		this.question = question;
	}

	public void ask() {
		System.out.println(name + "的问题是：" + this.question);
	}

	public String getName() {
		return name;
	}

}




package cn.com.ld.study.thread;

import java.util.concurrent.CountDownLatch;

/**   
 * @filename: AskJob   
 * @description: 提问线程 
 * @author lida  
 * @date 2013-3-29 下午1:34:42      
 */
public class AskJob extends Thread {
	private Reporter reporter;
	private CountDownLatch startMetting;
	private CountDownLatch endMetting;

	AskJob(Reporter reporter, CountDownLatch startMetting,
			CountDownLatch endMetting) {
		this.reporter = reporter;
		this.startMetting = startMetting;
		this.endMetting = endMetting;
	}

	public void run() {
		try {
			sleep(2000);
			startMetting.await();
			reporter.ask();
			endMetting.countDown();

		} catch (InterruptedException e) {
			e.printStackTrace();
			Thread.currentThread().interrupt();
		}
	}
}



package cn.com.ld.study.thread;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CountDownLatch;

/**   
 * @filename: ReporterMetting   
 * @description: 会议现场
 * @author lida  
 * @date 2013-3-29 下午1:35:20      
 */
public class ReporterMetting extends Thread {

	private int reporeterNo;
	private CountDownLatch startMetting;
	private CountDownLatch endMetting;
	private List<Reporter> repList;

	ReporterMetting(int reporeterNo, List<Reporter> repList,
			CountDownLatch start) {
		this.reporeterNo = repList.size();
		this.repList = repList;
		this.startMetting = start;
		this.endMetting = new CountDownLatch(reporeterNo);
	}

	public void run() {
		System.out.println("-----Metting is start----");
		AskJob aj = null;
		for (int i = 0; i < this.reporeterNo; i++) {
			Reporter reporter = repList.get(i);
			aj = new AskJob(reporter, startMetting, endMetting);
			aj.start();
		}
		// 待所有的问题准备就绪后，会议真正的开始
		startMetting.countDown();
		try {
			// 等待askjob 全部执行完毕唤醒 结束会议通知
			endMetting.await();
			System.out.println("-----Metting is end----");
		} catch (InterruptedException e) {
			e.printStackTrace();
		}

	}

	public static void main(String[] args) {
		List<Reporter> repList = new ArrayList<Reporter>();
		int reporeterNo = 10;
		Reporter reporter;
		for (int i = 1; i <= reporeterNo; i++) {
			reporter = new Reporter("狗仔" + i + "号", "开了" + i + "几瓶茅台，够不够喝？");
			repList.add(reporter);
		}
		CountDownLatch startMetting = new CountDownLatch(1);
		ReporterMetting rm = new ReporterMetting(reporeterNo, repList,
				startMetting);
		rm.start();

	}

}

测试结果:
-----Metting is start----
狗仔2号的问题是：开了2几瓶茅台，够不够喝？
狗仔5号的问题是：开了5几瓶茅台，够不够喝？
狗仔6号的问题是：开了6几瓶茅台，够不够喝？
狗仔3号的问题是：开了3几瓶茅台，够不够喝？
狗仔8号的问题是：开了8几瓶茅台，够不够喝？
狗仔4号的问题是：开了4几瓶茅台，够不够喝？
狗仔1号的问题是：开了1几瓶茅台，够不够喝？
狗仔7号的问题是：开了7几瓶茅台，够不够喝？
狗仔10号的问题是：开了10几瓶茅台，够不够喝？
狗仔9号的问题是：开了9几瓶茅台，够不够喝？
-----Metting is end----