主线程等待线程池所有任务完成

用线程池编写多线程程序时，当所有任务完成时，要做一些统计的工作。而统计工作必须要在所有任务完成才能做。所以要让主线程等待所有任务完成。可以使用ThreadPoolExecutor.awaitTermination(long timeout, TimeUnit unit)。请看示例代码：

package com.chenlb;

import java.util.Random;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

/**
* 线程池使用示例, 主线程等待所有任务完成再结束.
*
* @author chenlb 2008-12-2 上午10:31:03
*/
public class ThreadPoolUse {

public static class MyTask implements Runnable {
private static int id = 0;

private String name = "task-"+(++id);
private int sleep;

public MyTask(int sleep) {
super();
this.sleep = sleep;
}

public void run() {
System.out.println(name+" -----start-----");
try {
Thread.sleep(sleep); //模拟任务执行.
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(name+" -----end "+sleep+"-----");
}

}

public static void main(String[] args) {
System.out.println("==================start==================");
ThreadPoolExecutor executor = new ThreadPoolExecutor(5,5, 60, TimeUnit.SECONDS, new LinkedBlockingQueue());
int n = 10;
int sleep = 10 * 1000; //10s
Random rm = new Random();
for(int i=0; i executor.execute(new MyTask(rm.nextInt(sleep)+1));
}

executor.shutdown();

try {
boolean loop = true;
do { //等待所有任务完成
loop = !executor.awaitTermination(2, TimeUnit.SECONDS);
} while(loop);
} catch (InterruptedException e) {
e.printStackTrace();
}

System.out.println("==================end====================");
}

}
当然还有其它方法。

作者“thinking in hadoop”