CountDownLatch是java.util.concurrent包中一个类,CountDownLatch只要提供的机制是多个(具体数量等于初始化CountDownLatch时count的值)线程都达到了预期状态或者完成了预期工作时触发事件,其他线程可以等待这个事件来触发自己后续的工作。等待的线程可以是多个,即CountDownLatch可以唤醒多个等待的线程。到达自己预期状态的线程会调用CountDownLatch的countDown方法,而等待的线程会调用CountDownLatch的await方法。
什么情况下可以用这个cdl呢?我平常约朋友们打英雄联盟(5V5竞技游戏),然后总有那么一个人要在大家都上号了之后他才上号,这个情形就可以使用CDL来表示,废话不说直接上demo!
Player类作为我们提前上号的好队友,因为tx这垃圾服务器的存在,所以上号需要一定时间,这里随机数设置为等待0-10s~
public class Player implements Runnable { private CountDownLatch downLatch; private String name; public Player(CountDownLatch downLatch, String name) { this.downLatch = downLatch; this.name = name; } public void run() { this.doWork(); try { TimeUnit.SECONDS.sleep(new Random().nextInt(10)); } catch (Exception e) { } System.out.println(this.name + "已经上号了!"); this.downLatch.countDown(); } private void doWork() { System.out.println(this.name + "正在上号!"); } }
BadPlayer作为等大家都上了号以后,才上号那个拖延症坏队友
public class BadPlayer implements Runnable { private CountDownLatch downLatch; public BadPlayer(CountDownLatch downLatch){ this.downLatch = downLatch; } public void run() { System.out.println("拖延症玩家等其他队友都上号....."); try { this.downLatch.await(); } catch (Exception e) { } System.out.println("其他队友都上号了,他终于上号了~!!"); } }
主方法
public class CountDownLatchDemo { public static void main(String[] args) { ThreadPoolExecutor executor = new ThreadPoolExecutor(5, 5, 5, TimeUnit.SECONDS, new ArrayBlockingQueue(16)); CountDownLatch latch = new CountDownLatch(3); Player p1 = new Player(latch, "盖伦"); Player p2 = new Player(latch, "瑞兹"); Player p3 = new Player(latch, "娑娜"); Player p4 = new Player(latch, "赵信"); BadPlayer badPlayer = new BadPlayer(latch); executor.execute(p3); executor.execute(p2); executor.execute(p1); executor.execute(p4); executor.execute(badPlayer); executor.shutdown(); } }
shift+F10执行方法
搞定~
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