比如现在有10个线程，但每次只想运行3个线程，当这3个线程中的任何一个运行完后，第4个线程接着补上。这种情况可以使用线程池来解决，线程池用起来也相当的简单，不信，你看：
package com.demo;
import java.util.ArrayList;
import java.util.Collection;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class ThreadPool {
private int threadCount = 10;
private int threadpoolCount = 3;
public void threadPoolControl() {
ThreadObject[] et = new ThreadObject[threadCount];
ExecutorService service = Executors.newFixedThreadPool(threadpoolCount);
Collection<ThreadObject> c = new ArrayList<ThreadObject>();
for (int i = 0; i < threadCount; i++) {
et[i] = new ThreadObject();
c.add(et[i]);
}
try {
service.invokeAll(c);
service.shutdown();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
再加上ThreadObject类，这个类主要是线程的具体实现方法：
package com.demo;
import java.util.concurrent.Callable;
public class ThreadObject implements Callable<Object>{
public Object call() throws Exception {
//do something......
return null;
}
}
原文：http://www.cnblogs.com/zhangfei/p/4397536.html