java多线程-等候所有线程执行结束后再继续执行主线程

java多线程-等待所有线程执行结束后再继续执行主线程

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. ??????
13. ??????
14. ????static?class?Worker?extends?Thread{??
15. ????????String?workerName;???
16. ????????int?workTime;??
17. ????????CountDownLatch?latch;??
18. ????????public?Worker(String?workerName?,int?workTime?,CountDownLatch?latch){??
19. ?????????????this.workerName=workerName;??
20. ?????????????this.workTime=workTime;??
21. ?????????????this.latch=latch;??
22. ????????}??
23. ????????public?void?run(){??
24. ????????????System.out.println("Worker?"+workerName+"?do?work?begin?at?"+sdf.format(new?Date()));??
25. ????????????doWork();//工作了??
26. ????????????System.out.println("Worker?"+workerName+"?do?work?complete?at?"+sdf.format(new?Date()));??
27. ????????????latch.countDown();//工人完成工作，计数器减一??
28. ??
29. ????????}??
30. ??????????
31. ????????private?void?doWork(){??
32. ????????????try?{??
33. ????????????????Thread.sleep(workTime);??
34. ????????????}?catch?(InterruptedException?e)?{??
35. ????????????????e.printStackTrace();??
36. ????????????}??
37. ????????}??
38. ????}??
39. ??????
40. ???????
41. }??

?

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