Java并发程序设计(20)并发锁之倒数锁CountDownLatch

Posted 2020-09-07

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1.1. 倒数锁CountDownLatch

CountDownLatch是另外一种线程同步工具。参与倒数的每个线程在工作完成后都执行countDown()方法，当所有线程都执行完后，会唤醒一个或多个在等待倒数计数为0的线程。

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个倒数线程。

for(int i=0;i<10;i++){

executorService.submit(new Runnable(){

 

@Override

public void run() {

try {

Thread.sleep(1000* new Random().nextInt(20));

} catch (InterruptedException  e) {

e.printStackTrace();

}

//每个参与倒数的线程都倒数1次，计数减1.

countDownLatch.countDown();

System.out.println("count:" + countDownLatch.getCount() + " , " + new Date());

 

}

 

});

}

//建立3个等待倒数计数为0的线程。

for(int i=0;i<3;i++){

executorService.submit(new Runnable(){

 

@Override

public void run() {

try {

countDownLatch.await();

} catch (InterruptedException e) {

e.printStackTrace();

}

System.out.println("ready:" + countDownLatch.getCount() + " , " + new Date());

 

}

 

});

}

 

 

executorService.shutdown();

 

 

}

 

}