参考:http://www.importnew.com/21889.html
CountDownLatch
countDown() 方法执行完只是计数器减一, 并不会阻塞当前运行线程的的后续代码执行.
1 package org.wzh.demo.demo1; 2 3 import java.util.Random; 4 import java.util.concurrent.CountDownLatch; 5 6 public class D4CountDownLatch { 7 8 class Task extends Thread { 9 10 private CountDownLatch latch; 11 12 public Task(CountDownLatch latch) { 13 super(); 14 this.latch = latch; 15 } 16 17 @Override 18 public void run() { 19 // TODO Auto-generated method stub 20 try { 21 int time = (new Random().nextInt(8000) + 10000) / 1000; 22 System.out.println(Thread.currentThread().getName() + " 预计成绩 " + time + " seconds"); 23 Thread.sleep(time * 1000); 24 latch.countDown();//*** 25 System.out.println(Thread.currentThread().getName() + " 到达终点!"); 26 synchronized (latch) { 27 System.out.println("~~~~~~~~"); 28 System.out.println(Thread.currentThread().getName()); 29 System.out.println("~~~~~~~~"); 30 } 31 } catch (InterruptedException e) { 32 // TODO Auto-generated catch block 33 e.printStackTrace(); 34 } 35 36 } 37 38 } 39 40 public static void main(String[] args) throws InterruptedException { 41 CountDownLatch latch = new CountDownLatch(3);//*** 42 43 System.out.println("百米赛跑比赛开始"); 44 45 System.out.println("参赛选手:"); 46 String[] names = {"小明", "小强", "小智"}; 47 for (String name : names) { 48 System.out.println("\t" + name); 49 } 50 51 for (int i = 0; i < 3; i++) { 52 Thread t = new D4CountDownLatch().new Task(latch); 53 t.setName(names[i]); 54 t.start(); 55 } 56 latch.await();//*** 57 Thread.sleep(500); 58 System.out.println("百米赛跑比赛结束"); 59 } 60 61 }
百米赛跑比赛开始 参赛选手: 小明 小强 小智 小智 预计成绩 10 seconds 小明 预计成绩 14 seconds 小强 预计成绩 14 seconds 小智 到达终点! ~~~~~~~~ 小智 ~~~~~~~~ 小强 到达终点! ~~~~~~~~ 小强 小明 到达终点! ~~~~~~~~ ~~~~~~~~ 小明 ~~~~~~~~ 百米赛跑比赛结束
CyclicBarrier
await() 方法阻塞后面的代码,直到达到条件才继续向下执行.
1 package org.wzh.demo.demo1; 2 3 import java.util.Random; 4 import java.util.concurrent.BrokenBarrierException; 5 import java.util.concurrent.CyclicBarrier; 6 7 8 public class D4CyclicBarrier { 9 10 class Task extends Thread { 11 12 private CyclicBarrier barrier; 13 14 public Task(CyclicBarrier barrier) { 15 super(); 16 this.barrier = barrier; 17 } 18 19 @Override 20 public void run() { 21 // TODO Auto-generated method stub 22 try { 23 int time = (new Random().nextInt(8000) + 10000) / 1000; 24 System.out.println(Thread.currentThread().getName() + " 预计成绩 " + time + " seconds"); 25 Thread.sleep(time * 1000); 26 System.out.println(Thread.currentThread().getName() + " 到达终点!"); 27 barrier.await();//*** 28 synchronized (barrier) { 29 System.out.println("~~~~~~~~"); 30 System.out.println(Thread.currentThread().getName()); 31 System.out.println("~~~~~~~~"); 32 } 33 } catch (InterruptedException e) { 34 // TODO Auto-generated catch block 35 e.printStackTrace(); 36 } catch (BrokenBarrierException e) { 37 // TODO Auto-generated catch block 38 e.printStackTrace(); 39 } 40 } 41 42 } 43 44 public static void main(String[] args) { 45 try { 46 CyclicBarrier barrier = new CyclicBarrier(4);//*** 47 48 System.out.println("百米赛跑比赛开始"); 49 String[] names = {"小明", "小强", "小智"}; 50 System.out.println("参赛选手:"); 51 for (String name : names) { 52 System.out.println("\t" + name); 53 } 54 for (int i = 0; i < 3; i++) { 55 Thread t = new D4CyclicBarrier().new Task(barrier); 56 t.setName(names[i]); 57 t.start(); 58 } 59 barrier.await(); 60 Thread.sleep(500); 61 System.out.println("百米赛跑比赛结束"); 62 } catch (Exception e) { 63 e.printStackTrace(); 64 } 65 } 66 67 }
百米赛跑比赛开始 参赛选手: 小明 小强 小智 小明 预计成绩 12 seconds 小强 预计成绩 14 seconds 小智 预计成绩 10 seconds 小智 到达终点! 小明 到达终点! 小强 到达终点! ~~~~~~~~ 小智 ~~~~~~~~ ~~~~~~~~ 小明 ~~~~~~~~ ~~~~~~~~ Сǿ ~~~~~~~~ 百米赛跑比赛结束
区别
CountDownLatch和CyclicBarrier都能够实现线程之间的等待，只不过它们侧重点不同：
CountDownLatch一般用于某个线程A等待若干个其他线程执行完任务之后，它才执行；
而CyclicBarrier一般用于一组线程互相等待至某个状态，然后这一组线程再同时执行；
另外，CountDownLatch是不能够重用的，而CyclicBarrier是可以重用的。