Java並發程式設計(20)並發鎖之倒數鎖CountDownLatch

標籤：喚醒   out   線程   dom   style   print   countdown   cst   ready   

1.1. 倒數鎖CountDownLatch

 

CountDownLatch是另外一種線程同步工具。參與倒數的每個線程在工作完成後都執行countDown()方法，當所有線程都執行完後，會喚醒一個或多個在等待倒數計數為0的線程。

 

 

package com.test.concurrence; import java.util.Date;import java.util.Random;import java.util.concurrent.CountDownLatch;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors; public class CountDownLatchTest { public static void main(String[] args) { final CountDownLatch  countDownLatch = new CountDownLatch(10);ExecutorService  executorService = Executors.newFixedThreadPool(10);//建立10個倒數線程。for(int i=0;i<10;i++){executorService.submit(new Runnable(){ @Overridepublic void run() {try {Thread.sleep(1000* new Random().nextInt(20));} catch (InterruptedException  e) {e.printStackTrace();}//每個參與倒數的線程都倒數1次，計數減1.countDownLatch.countDown();System.out.println("count:" + countDownLatch.getCount() + " , " + new Date()); } });}//建立3個等待倒數計數為0的線程。for(int i=0;i<3;i++){executorService.submit(new Runnable(){ @Overridepublic void run() {try {countDownLatch.await();} catch (InterruptedException e) {e.printStackTrace();}System.out.println("ready:" + countDownLatch.getCount() + " , " + new Date()); } });}  executorService.shutdown();  } } 

 

運行結果如下：

count:9 , Sat Mar 18 23:11:16 CST 2017

count:7 , Sat Mar 18 23:11:18 CST 2017

count:8 , Sat Mar 18 23:11:18 CST 2017

count:6 , Sat Mar 18 23:11:20 CST 2017

count:5 , Sat Mar 18 23:11:25 CST 2017

count:4 , Sat Mar 18 23:11:25 CST 2017

count:3 , Sat Mar 18 23:11:26 CST 2017

count:2 , Sat Mar 18 23:11:27 CST 2017

count:1 , Sat Mar 18 23:11:33 CST 2017

count:0 , Sat Mar 18 23:11:33 CST 2017

ready:0 , Sat Mar 18 23:11:33 CST 2017

ready:0 , Sat Mar 18 23:11:33 CST 2017

ready:0 , Sat Mar 18 23:11:33 CST 2017

 

Java並發程式設計(20)並發鎖之倒數鎖CountDownLatch