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。

时间:2022-08-30 13:50:52

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);

public void countDown();

public void await() throws InterruptedException

构造方法参数指定了计数的次数

countDown方法,当前线程调用此方法,则计数减一

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

例子

  1. public class CountDownLatchDemo {
  2. final static SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
  3. public static void main(String[] args) throws InterruptedException {
  4. CountDownLatch latch=new CountDownLatch(2);//两个工人的协作
  5. Worker worker1=new Worker("zhang san", 5000, latch);
  6. Worker worker2=new Worker("li si", 8000, latch);
  7. worker1.start();//
  8. worker2.start();//
  9. latch.await();//等待所有工人完成工作
  10. System.out.println("all work done at "+sdf.format(new Date()));
  11. }
  12. static class Worker extends Thread{
  13. String workerName;
  14. int workTime;
  15. CountDownLatch latch;
  16. public Worker(String workerName ,int workTime ,CountDownLatch latch){
  17. this.workerName=workerName;
  18. this.workTime=workTime;
  19. this.latch=latch;
  20. }
  21. public void run(){
  22. System.out.println("Worker "+workerName+" do work begin at "+sdf.format(new Date()));
  23. doWork();//工作了
  24. System.out.println("Worker "+workerName+" do work complete at "+sdf.format(new Date()));
  25. latch.countDown();//工人完成工作,计数器减一
  26. }
  27. private void doWork(){
  28. try {
  29. Thread.sleep(workTime);
  30. } catch (InterruptedException e) {
  31. e.printStackTrace();
  32. }
  33. }
  34. }
  35. }

输出:

Worker zhang san do work begin at 2011-04-14 11:05:11
Worker li si do work begin at 2011-04-14 11:05:11
Worker zhang san do work complete at 2011-04-14 11:05:16
Worker li si do work complete at 2011-04-14 11:05:19
all work done at 2011-04-14 11:05:19