如何判断java多线程是否全部执行完了，并计 怎么知道java多线程都已经运行结束
java\u591a\u7ebf\u7a0b\u4e2d\uff0c\u600e\u6837\u77e5\u9053\u7ebf\u7a0b\u6267\u884c\u7ed3\u675f\u5728\u4f60\u7684\u4e3b\u7ebf\u7a0b\u4e2d\u7528\u4e00\u4e2ajoin\u7684\u65b9\u6cd5\uff0c\u4f60\u8981\u7b49\u5f85\u8c01\uff0c\u5c31\u7528\u8c01\u8c03\u7528\uff0c\u6bd4\u5982\uff0c\u4f60\u8981\u7b49\u5f85\u7ebf\u7a0ba\u7ed3\u675f\uff0c\u5c31\u7528a.join();\u8fd9\u6837\u5c31\u53ef\u4ee5\u4e86\u3002\u8bb0\u4f4f\u54e6\uff0c\u8fd9\u6761\u8bed\u53e5\u5199\u5728\u54ea\u4e2a\u7ebf\u7a0b\u91cc\uff0c\u54ea\u4e2a\u7ebf\u7a0b\u5c31\u8981\u7b49\u5f85\u8c03\u7528\u8fd9\u4e2a\u65b9\u6cd5\u7684\u5176\u4ed6\u7ebf\u7a0b\u3002\u5c31\u662f\u8bf4\uff0c\u4f60\u5728\u4e3b\u7ebf\u7a0b\u91cc\u5199\u4e86\u8fd9\u6761\u8bed\u53e5\uff0c\u90a3\u4e48\u4e3b\u7ebf\u7a0b\u5c31\u8981\u7b49\u5f85\u7ebf\u7a0ba\u6267\u884c\u5b8c\u540e\uff0c\u4e3b\u7ebf\u7a0b\u624d\u4f1a\u6267\u884c\u3002
\u4e00\u3001\u4f7f\u7528java.util.concurrent.CountDownLatch
Java\u7684util.concurrent\u5305\u91cc\u9762\u7684CountDownLatch\u5176\u5b9e\u53ef\u4ee5\u628a\u5b83\u770b\u4f5c\u4e00\u4e2a\u8ba1\u6570\u5668\uff0c\u53ea\u4e0d\u8fc7\u8fd9\u4e2a\u8ba1\u6570\u5668\u7684\u64cd\u4f5c\u662f\u539f\u5b50\u64cd\u4f5c\uff0c\u540c\u65f6\u53ea\u80fd\u6709\u4e00\u4e2a\u7ebf\u7a0b\u53bb\u64cd\u4f5c\u8fd9\u4e2a\u8ba1\u6570\u5668\uff0c\u4e5f\u5c31\u662f\u540c\u65f6\u53ea\u80fd\u6709\u4e00\u4e2a\u7ebf\u7a0b\u53bb\u51cf\u8fd9\u4e2a\u8ba1\u6570\u5668\u91cc\u9762\u7684\u503c\u3002
\u4f60\u53ef\u4ee5\u5411CountDownLatch\u5bf9\u8c61\u8bbe\u7f6e\u4e00\u4e2a\u521d\u59cb\u7684\u6570\u5b57\u4f5c\u4e3a\u8ba1\u6570\u503c\uff0c\u4efb\u4f55\u8c03\u7528\u8fd9\u4e2a\u5bf9\u8c61\u4e0a\u7684await()\u65b9\u6cd5\u90fd\u4f1a\u963b\u585e\uff0c\u76f4\u5230\u8fd9\u4e2a\u8ba1\u6570\u5668\u7684\u8ba1\u6570\u503c\u88ab\u5176\u4ed6\u7684\u7ebf\u7a0b\u51cf\u4e3a0\u4e3a\u6b62\u3002
CountDownLatch\u7684\u4e00\u4e2a\u975e\u5e38\u5178\u578b\u7684\u5e94\u7528\u573a\u666f\u662f\uff1a\u6709\u4e00\u4e2a\u4efb\u52a1\u60f3\u8981\u5f80\u4e0b\u6267\u884c\uff0c\u4f46\u5fc5\u987b\u8981\u7b49\u5230\u5176\u4ed6\u7684\u4efb\u52a1\u6267\u884c\u5b8c\u6bd5\u540e\u624d\u53ef\u4ee5\u7ee7\u7eed\u5f80\u4e0b\u6267\u884c\u3002\u5047\u5982\u6211\u4eec\u8fd9
\u4e2a\u60f3\u8981\u7ee7\u7eed\u5f80\u4e0b\u6267\u884c\u7684\u4efb\u52a1\u8c03\u7528\u4e00\u4e2aCountDownLatch\u5bf9\u8c61\u7684await()\u65b9\u6cd5\uff0c\u5176\u4ed6\u7684\u4efb\u52a1\u6267\u884c\u5b8c\u81ea\u5df1\u7684\u4efb\u52a1\u540e\u8c03\u7528\u540c\u4e00\u4e2a
CountDownLatch\u5bf9\u8c61\u4e0a\u7684countDown()\u65b9\u6cd5\uff0c\u8fd9\u4e2a\u8c03\u7528await()\u65b9\u6cd5\u7684\u4efb\u52a1\u5c06\u4e00\u76f4\u963b\u585e\u7b49\u5f85\uff0c\u76f4\u5230\u8fd9\u4e2a
CountDownLatch\u5bf9\u8c61\u7684\u8ba1\u6570\u503c\u51cf\u52300\u4e3a\u6b62\u3002
\u4e3e\u4e2a\u4f8b\u5b50\uff0c\u6709\u4e09\u4e2a\u5de5\u4eba\u5728\u4e3a\u8001\u677f\u5e72\u6d3b\uff0c\u8fd9\u4e2a\u8001\u677f\u6709\u4e00\u4e2a\u4e60\u60ef\uff0c\u5c31\u662f\u5f53\u4e09\u4e2a\u5de5\u4eba\u628a\u4e00\u5929\u7684\u6d3b\u90fd
\u5e72\u5b8c\u4e86\u7684\u65f6\u5019\uff0c\u4ed6\u5c31\u6765\u68c0\u67e5\u6240\u6709\u5de5\u4eba\u6240\u5e72\u7684\u6d3b\u3002\u8bb0\u4f4f\u8fd9\u4e2a\u6761\u4ef6\uff1a\u4e09\u4e2a\u5de5\u4eba\u5148\u5168\u90e8\u5e72\u5b8c\u6d3b\uff0c\u8001\u677f\u624d\u68c0\u67e5\u3002\u6240\u4ee5\u5728\u8fd9\u91cc\u7528Java\u4ee3\u7801\u8bbe\u8ba1\u4e24\u4e2a\u7c7b\uff0cWorker\u4ee3\u8868\u5de5
\u4eba\uff0cBoss\u4ee3\u8868\u8001\u677f\uff0c\u5177\u4f53\u7684\u4ee3\u7801\u5b9e\u73b0\u5982\u4e0b\uff1a
Worker\u7c7b\uff08\u5355\u72ec\u7684\u7ebf\u7a0b\uff09\uff1a
package cn.edu.bupt.thread.threadnotify;
import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
public class Worker implements Runnable
{
private CountDownLatch downLatch;
private String name;
public Worker(CountDownLatch downLatch, String name)
{
this.downLatch = downLatch;
this.name = name;
}
@Override
public void run()
{
this.doWork();
try
{
TimeUnit.SECONDS.sleep(new Random().nextInt(10));
}
catch (InterruptedException ie)
{
}
System.out.println(this.name + "\u6d3b\u5e72\u5b8c\u4e86\uff01");
this.downLatch.countDown();
}
private void doWork()
{
System.out.println(this.name + "\u6b63\u5728\u5e72\u6d3b...");
}
}
Boss\u7c7b\uff08\u5355\u72ec\u7684\u7ebf\u7a0b\uff09\uff1a
package cn.edu.bupt.thread.threadnotify;
import java.util.concurrent.CountDownLatch;
public class Boss implements Runnable
{
private CountDownLatch downLatch;
public Boss(CountDownLatch downLatch)
{
this.downLatch = downLatch;
}
@Override
public void run()
{
System.out.println("\u8001\u677f\u6b63\u5728\u7b49\u6240\u6709\u7684\u5de5\u4eba\u5e72\u5b8c\u6d3b......");
try
{
this.downLatch.await();
}
catch (InterruptedException e)
{
}
System.out.println("\u5de5\u4eba\u6d3b\u90fd\u5e72\u5b8c\u4e86\uff0c\u8001\u677f\u5f00\u59cb\u68c0\u67e5\u4e86\uff01");
}
}
Main\uff1a
package cn.edu.bupt.thread.threadnotify;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class CountDownLatchDemo
{
public static void main(String[] args)
{
ExecutorService executor = Executors.newCachedThreadPool();
CountDownLatch latch = new CountDownLatch(3);
Worker w1 = new Worker(latch, "\u5f20\u4e09");
Worker w2 = new Worker(latch, "\u674e\u56db");
Worker w3 = new Worker(latch, "\u738b\u4e8c");
Boss boss = new Boss(latch);
executor.execute(boss);
executor.execute(w3);
executor.execute(w2);
executor.execute(w1);
executor.shutdown();
}
}
\u4e0a\u4f8b\u4e2d\u7684\u7684ExecutorService\u63a5\u53e3\u548cExecutors\u7c7b\u7684\u4f5c\u7528\u7c7b\u4f3c\u4e8enew Thread(Runnable r).start()\u7684\u4f5c\u7528\uff0c\u5c31\u662f\u542f\u52a8\u4e00\u4e2a\u65b0\u7684\u7ebf\u7a0b\u3002
步骤：
1： 创建线程池 ExecutorService cachedThreadPool
2： 开启一个线程 cachedThreadPool.execute(new Runnable() ｛//做任务｝）
3.： 判断线程池里面是否执行完， cachedThreadPool.isTerminated()
while (true) {
if (cachedThreadPool.isTerminated()) { // 计算耗时
long time = System.currentTimeMillis() - start;
System.out.println("["+Utils.getNowTime()+"]:" + "程序结束了，总耗时：" + time + " ms(毫秒)！\n");
break;
}
}
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