public final class ThreadPool {// 线程池中默认线程的个数为5private static int worker_num = 5;// 工作线程private WorkThread[] workThreads;// 任务队列，作为一个缓冲,List线程不安全private List<Runnable> taskQueue = new LinkedList<Runnable>();private static ThreadPool threadPool;// 创建具有默认线程个数的线程池private ThreadPool() {this(5);}// 创建线程池,worker_num为线程池中工作线程的个数private ThreadPool(int worker_num) {ThreadPool.worker_num = worker_num;workThreads = new WorkThread[worker_num];for (int i = 0; i < worker_num; i++) {workThreads[i] = new WorkThread();workThreads[i].start();// 开启线程池中的线程
          }}// 单态模式，获得一个默认线程个数的线程池public static ThreadPool getThreadPool() {return getThreadPool(ThreadPool.worker_num);}// 单态模式，获得一个指定线程个数的线程池,worker_num(>0)为线程池中工作线程的个数// worker_num<=0创建默认的工作线程个数public static ThreadPool getThreadPool(int worker_num1) {if (threadPool == null)threadPool = new ThreadPool(worker_num1);return threadPool;}// 执行任务,其实只是把任务加入任务队列，什么时候执行有线程池管理器觉定public void addTask(Runnable task) {synchronized (taskQueue) {taskQueue.add(task);taskQueue. notifyAll();}}// 销毁线程池,该方法保证在所有任务都完成的情况下才销毁所有线程，否则等待任务完成才销毁public void destroy() {while (!taskQueue.isEmpty()) {// 如果还有任务没执行完成，就先睡会吧try {Thread.sleep(10);} catch (InterruptedException e) {e.printStackTrace();}}// 工作线程停止工作，且置为nullfor (int i = 0; i < worker_num; i++) {workThreads[i].stopWorker();workThreads[i] = null;}threadPool=null;taskQueue.clear();// 清空任务队列
     }/*** 内部类，工作线程*/private class WorkThread extends Thread {// 该工作线程是否有效，用于结束该工作线程private boolean isRunning = true;/** 关键所在啊，如果任务队列不空，则取出任务执行，若任务队列空，则等待*/@Overridepublic void run() {Runnable r = null;while (isRunning) {// 注意，若线程无效则自然结束run方法，该线程就没用了
                    synchronized (taskQueue) {while (isRunning && taskQueue.isEmpty()) {// 队列为空try {taskQueue.wait(20);} catch (InterruptedException e) {e.printStackTrace();}}if (!taskQueue.isEmpty())r = taskQueue.remove(0);// 取出任务
                    }if (r != null) {r.run();// 执行任务
                    }r = null;}}// 停止工作，让该线程自然执行完run方法，自然结束public void stopWorker() {isRunning = false;}}
}