package aaa.bbb;

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

public class T1 {
	final static SimpleDateFormat sdf = new SimpleDateFormat(
			"yyyy-MM-dd HH:mm:ss");

	public static void main(String[] args) throws Exception {
		CountDownLatch countDownLatch = new CountDownLatch(3);
		Worker w1 = new Worker("w1", 2000, countDownLatch);
		Worker w2 = new Worker("w2", 5000, countDownLatch);
		w1.start();//
		w2.start();//
		countDownLatch.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;
		}

		@Override
		public void run() {
			System.out.println("Worker " + workerName + " do work begin at "
					+ sdf.format(new Date()));
			try {
				Thread.sleep(workTime);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			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
		}
	}
}

java countDownLatch 线程辅助类