用來干嘛的？當你在方法中調用了多個線程，對數(shù)據(jù)庫進行了一些不為人知的操作后，還有一個操作需要留到前者都執(zhí)行完的重頭戲，就需要用到 CountDownLatch 了

package com.github.gleans;import java.util.concurrent.CountDownLatch;public class TestCountDownLatch { public static void main(String[] args) throws InterruptedException { CountDownLatch latch = new CountDownLatch(3); new KeyPass(1000L, 'thin jack', latch).start(); new KeyPass(2000L, 'noral jack', latch).start(); new KeyPass(3000L, 'fat jack', latch).start(); latch.await(); System.out.println('此處對數(shù)據(jù)庫進行最后的插入操作~'); } static class KeyPass extends Thread { private long times; private CountDownLatch countDownLatch; public KeyPass(long times, String name, CountDownLatch countDownLatch) { super(name); this.times = times; this.countDownLatch = countDownLatch; } @Override public void run() { try {System.out.println('操作人：' + Thread.currentThread().getName() + '對數(shù)據(jù)庫進行插入，持續(xù)時間：' + this.times / 1000 + '秒');Thread.sleep(times);countDownLatch.countDown(); } catch (InterruptedException e) {e.printStackTrace(); } } }}圖解

使用await()提前結束操作

package com.github.gleans;import java.util.concurrent.CountDownLatch;import java.util.concurrent.TimeUnit;public class TestCountDownLatch { public static void main(String[] args) throws InterruptedException { CountDownLatch latch = new CountDownLatch(3); new KeyPass(2000L, '公司一', latch).start(); new KeyPass(3000L, '公司二', latch).start(); new KeyPass(5000L, '公司三', latch).start(); latch.await(2, TimeUnit.SECONDS); System.out.println('~~~賈總PPT巡演~~~~'); System.out.println('~~~~融資完成，撒花~~~~'); } static class KeyPass extends Thread { private long times; private CountDownLatch countDownLatch; public KeyPass(long times, String name, CountDownLatch countDownLatch) { super(name); this.times = times; this.countDownLatch = countDownLatch; } @Override public void run() { try {Thread.sleep(times);System.out.println('負責人：' + Thread.currentThread().getName() + '開始工作，持續(xù)時間：' + this.times / 1000 + '秒');countDownLatch.countDown(); } catch (InterruptedException e) {e.printStackTrace(); } } }}

假設公司一、公司二、公司三各需要2s、3s、5s來完成工作，賈總等不了，只能等2s，那么就設置await的超時時間

latch.await(2, TimeUnit.SECONDS);執(zhí)行結果

負責人：公司一開始工作，持續(xù)時間：2秒~~~賈總PPT巡演~~~~~~~~融資完成，撒花~~~~負責人：公司二開始工作，持續(xù)時間：3秒負責人：公司三開始工作，持續(xù)時間：5秒

方法描述

這個操作可以說是簡單好用，目前還未遇見副作用，若是有大佬，可以告知弟弟一下，提前表示感謝~

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