Java多线程协作CountDownLatch,主线程等待子线程结束

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() 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

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    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();
                }
            }
        }  

    }