利用CountDownLatch实现的一个简单的线程同步场景

package countdownlatchTest;

import java.util.concurrent.CountDownLatch;

class Worker {
private String name;        // 名字
private long workDuration;  // 工作持续时间
public Worker(String name, long workDuration) {
this.name = name;
this.workDuration = workDuration;
System.out.println("Worker: " + name + " is assigned with work time: " + workDuration);
}

public void doWork() {
System.out.println(name + " begins to work...");
try {
Thread.sleep(workDuration); // 用休眠模拟工作执行的时间
} catch(InterruptedException ex) {
ex.printStackTrace();
}
System.out.println(name + " has finished the job...");
}
}

class WorkerTestThread implements Runnable {
private Worker worker;
private CountDownLatch cdLatch;
public WorkerTestThread(Worker worker, CountDownLatch cdLatch) {
this.worker = worker;
this.cdLatch = cdLatch;
}

@Override
public void run() {
worker.doWork();        // 让工人开始工作
cdLatch.countDown();    // 工作完成后倒计时次数减1
}

}

public class CountDownLatchTest {
private static final int MAX_WORK_DURATION = 5000;  // 最大工作时间
private static final int MIN_WORK_DURATION = 1000;  // 最小工作时间
// 产生随机的工作时间
private static long getRandomWorkDuration(long min, long max) {
return (long) (Math.random() * (max - min) + min);
}

public static void main(String[] args) {
/* 2是次数，不是时间数
* 将这个CountDownLatch引用赋给工作线程，每次工作线程完成任务后，调用
* CountDownLatch.countDown, 将计数器减一。如果技术器减到0，阻塞的await方法
* 才会返回，重新获得控制权
*/
CountDownLatch latch = new CountDownLatch(2);  // should be exactly 2
Worker w1 = new Worker("Jerry Worker 1", getRandomWorkDuration(MIN_WORK_DURATION, MAX_WORK_DURATION));
Worker w2 = new Worker("Jerry Worker 2", getRandomWorkDuration(MIN_WORK_DURATION, MAX_WORK_DURATION));
new Thread(new WorkerTestThread(w1, latch)).start();
new Thread(new WorkerTestThread(w2, latch)).start();
// latch.countDown();
try {
// 仅当CountDownLatch的count降低到0时，这个阻塞的方法才会返回
latch.await();
System.out.println("All jobs have been finished!");
}
catch (InterruptedException e) {
e.printStackTrace();
}
}
}