場景：需要啟動多線程處理事情，而在所有事情做完之后，需要修改系統狀態；那么如何判斷所有線程（事情）都做完了呢？這就需要判斷所有當前運行的線程狀態了。
代碼 import?java.util.concurrent.CountDownLatch;
import?java.util.concurrent.Executor;
import?java.util.concurrent.Executors;

/** 測試監控類?*/
public?class?WatchThread?{

????/**?測試函數 */
????public?void?testThread()?throws?InterruptedException?{
????????int?threadNum?=?10;
????????//?初始化countDown
????????CountDownLatch?threadSignal?=?new?CountDownLatch(threadNum);
????????//?創建固定長度的線程池
????????Executor?executor?=?Executors.newFixedThreadPool(threadNum);
????????for?(int?i?=?0;?i?<?threadNum;?i++)?{?//?開threadNum個線程
????????????Runnable?task?=?new?TestThread(threadSignal);
????????????//?執行
????????????executor.execute(task);
????????}
????????threadSignal.await();?//?等待所有子線程執行完
????????//?do?work
????????System.out.println(Thread.currentThread().getName()?+?"+++++++結束.");
????}

????/**?測試函數?*/
????public?static?void?main(String[]?args)?throws?InterruptedException?{
????????WatchThread?test?=?new?WatchThread();
????????test.testThread();
????}
????private?class?TestThread?implements?Runnable?{
????????private?CountDownLatch?threadsSignal;

????????public?TestThread(CountDownLatch?threadsSignal)?{
????????????this.threadsSignal?=?threadsSignal;
????????}

????????public?void?run()?{
????????????System.out.println(Thread.currentThread().getName()?+?"開始...");
????????????//?do?shomething
????????????System.out.println("開始了線程：：：："?+?threadsSignal.getCount());
????????????//?線程結束時計數器減1
????????????threadsSignal.countDown();
????????????System.out.println(Thread.currentThread().getName()?+?"結束.?還有"
????????????????????+?threadsSignal.getCount()?+?"?個線程");
????????}
????}

}

?

轉載于:https://www.cnblogs.com/MyFavorite/archive/2010/10/15/1852567.html

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