Java多线程协作CountDownLatch,主线程等待子线程结束

Posted 2020-08-15 swbzmx

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();  
                }  
            }  
        }  
          
           
    }