本文介绍两种主线程等待子线程的实现方式，以5个子线程来说明：
1、使用Thread的join()方法，join()方法会阻塞主线程继续向下执行。
2、使用Java.util.concurrent中的CountDownLatch，是一个倒数计数器。初始化时先设置一个倒数计数初始值，每调用一次countDown()方法，倒数值减一，他的await()方法会阻塞当前进程，直到倒数至0。
join方式代码如下：
- package com.test.thread;
-
- import java.util.ArrayList;
- import java.util.List;
-
- public class MyThread extends Thread
- {
-
- public MyThread(String name)
- {
- this.setName(name);
- }
-
- @Override
- public void run()
- {
- System.out.println(this.getName() + " staring...");
-
- System.out.println(this.getName() + " end...");
- }
-
-
- public static void main(String[] args)
- {
- System.out.println("main thread starting...");
-
- List<MyThread> list = new ArrayList<MyThread>();
-
- for (int i = 1; i <= 5; i++)
- {
- MyThread my = new MyThread("Thrad " + i);
- my.start();
- list.add(my);
- }
-
- try
- {
- for (MyThread my : list)
- {
- my.join();
- }
- }
- catch (InterruptedException e)
- {
- e.printStackTrace();
- }
-
- System.out.println("main thread end...");
-
- }
-
- }
运行结果如下：
main thread starting...
Thrad 2 staring...
Thrad 2 end...
Thrad 4 staring...
Thrad 4 end...
Thrad 1 staring...
Thrad 1 end...
Thrad 3 staring...
Thrad 3 end...
Thrad 5 staring...
Thrad 5 end...
main thread end...
CountDownLatch方式代码如下：
- package com.test.thread;
-
- import java.util.concurrent.CountDownLatch;
-
- public class MyThread2 extends Thread
- {
-
- private CountDownLatch count;
-
- public MyThread2(CountDownLatch count, String name)
- {
- this.count = count;
- this.setName(name);
- }
-
- @Override
- public void run()
- {
- System.out.println(this.getName() + " staring...");
-
- System.out.println(this.getName() + " end...");
- this.count.countDown();
- }
-
-
- public static void main(String[] args)
- {
- System.out.println("main thread starting...");
-
- CountDownLatch count = new CountDownLatch(5);
-
- for (int i = 1; i <= 5; i++)
- {
- MyThread2 my = new MyThread2(count, "Thread " + i);
- my.start();
- }
-
- try
- {
- count.await();
- }
- catch (InterruptedException e)
- {
- e.printStackTrace();
- }
-
- System.out.println("main thread end...");
-
- }
-
- }
运行结果如下：
main thread starting...
Thread 2 staring...
Thread 2 end...
Thread 4 staring...
Thread 4 end...
Thread 1 staring...
Thread 1 end...
Thread 3 staring...
Thread 3 end...
Thread 5 staring...
Thread 5 end...
main thread end...
Java实现主线程等待子线程
原文：http://www.cnblogs.com/toSeeMyDream/p/6959223.html
