java多线程之CountDownLatch类基本用法

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java.util.concurrent.CountDownLatch类是一个同步计数器,构造时传入int参数,该参数就是计数器的初始值，每调用一次countDown()方法，计数器减1,计数器大于0 时，await()方法会阻塞程序继续执行。
1.构造方法参数指定了计数的次数
2.countDown方法，当前线程调用此方法，则计数减一
3.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

package cn.baokx;import java.util.Random;import java.util.concurrent.CountDownLatch;import java.util.concurrent.TimeUnit;class SubThread implements Runnable{private CountDownLatch downLatch;private String name;public SubThread(CountDownLatch downLatch,String name){this.downLatch = downLatch;this.name = name;}@Overridepublic void run() {System.out.println(this.name+" is working...");try {TimeUnit.SECONDS.sleep(new Random().nextInt(10));System.out.println(this.name + " has finished its working...");} catch (InterruptedException e) {e.printStackTrace();}finally{this.downLatch.countDown();}}}public class CountDownLatchTest {public static void main(String[] args) {CountDownLatch downLatch = new CountDownLatch(4);SubThread st1 = new SubThread(downLatch,"subThread1");SubThread st2 = new SubThread(downLatch,"subThread2");SubThread st3 = new SubThread(downLatch,"subThread3");SubThread st4 = new SubThread(downLatch,"subThread4");System.out.println("MainThread is wating...");new Thread(st1).start();new Thread(st2).start();new Thread(st3).start();new Thread(st4).start();try {downLatch.await();} catch (InterruptedException e) {e.printStackTrace();}System.out.println("All subThread has finished,MainThread can begin to checking...");}}

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