1 import java.util.concurrent.CountDownLatch; 2 import java.util.concurrent.ExecutorService; 3 import java.util.concurrent.Executors; 4  5 /** 6  * 16.Java5的CountDownLatch同步工具 7  * 犹如倒计时计数器，调用CountDownLatch对象的CountDown方法就将计数器减1， 8  * 当计数到达0事，则所有等待者或单个等待着开始执行。 9  * 10  * @author LiTaiQing11  *12  */13 public class CountdownLatchTest {14 15     public static void main(String[] args) {16         ExecutorService service = Executors.newCachedThreadPool();17         final CountDownLatch cdOrder = new CountDownLatch(1);18         final CountDownLatch cdAnswer = new CountDownLatch(3);19         for (int i = 0; i < 3; i++) {20             Runnable runnable = new Runnable() {21                 public void run() {22                     try {23                         System.out.println("线程"24                                 + Thread.currentThread().getName() + "正准备接受命令");25                         cdOrder.await();26                         System.out.println("线程"27                                 + Thread.currentThread().getName() + "已接受命令");28                         Thread.sleep((long) (Math.random() * 10000));29                         System.out30                                 .println("线程"31                                         + Thread.currentThread().getName()32                                         + "回应命令处理结果");33                         cdAnswer.countDown();34                     } catch (Exception e) {35                         e.printStackTrace();36                     }37                 }38             };39             service.execute(runnable);40         }41         try {42             Thread.sleep((long) (Math.random() * 10000));43 44             System.out.println("线程" + Thread.currentThread().getName()45                     + "即将发布命令");46             cdOrder.countDown();47             System.out.println("线程" + Thread.currentThread().getName()48                     + "已发送命令，正在等待结果");49             cdAnswer.await();50             System.out.println("线程" + Thread.currentThread().getName()51                     + "已收到所有响应结果");52         } catch (Exception e) {53             e.printStackTrace();54         }55         service.shutdown();56 57     }58 }