任何游戏都至少需要运行两个线程,主线程和gui线程
而线程池是一个管理运行线程的有用工具,下面的代码示范了一个线程池的实现方法~~
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(threadpool.java)
import java.util.linkedlist;

/**
    线程池是一组线程，限制执行任务的线程数
*/
public class threadpool extends threadgroup {

    private boolean isalive;
    private linkedlist taskqueue;
    private int threadid;
    private static int threadpoolid;

    /**
        创建新的线程池，numthreads是池中的线程数
    */
    public threadpool(int numthreads) {
        super("threadpool-" + (threadpoolid++));
        setdaemon(true);

        isalive = true;

        taskqueue = new linkedlist();
        for (int i=0; i<numthreads; i++) {
            new pooledthread().start();
        }
    }
    /**
        请求新任务。人物在池中下一空闲线程中运行，任务按收到的顺序执行
    */
    public synchronized void runtask(runnable task) {
        if (!isalive) {
            throw new illegalstateexception();//线程被关则抛出illegalstateexception异常
        }
        if (task != null) {
            taskqueue.add(task);
            notify();
        }

    }

    protected synchronized runnable gettask()
        throws interruptedexception
    {
        while (taskqueue.size() == 0) {
            if (!isalive) {
                return null;
            }
            wait();
        }
        return (runnable)taskqueue.removefirst();
    }

    /**
        关闭线程池，所有线程停止，不再执行任务
    */
    public synchronized void close() {
        if (isalive) {
            isalive = false;
            taskqueue.clear();
            interrupt();
        }
    }

    /**
        关闭线程池并等待所有线程完成，执行等待的任务
    */
    public void join() {
        //告诉等待线程线程池已关
        synchronized (this) {
            isalive = false;
            notifyall();
        }

        // 等待所有线程完成
        thread[] threads = new thread[activecount()];
        int count = enumerate(threads);
        for (int i=0; i<count; i++) {
            try {
                threads[i].join();
            }
            catch (interruptedexception ex) { }
        }
    }

    /**
        用于进行任务的线程
    */
    private class pooledthread extends thread {

        public pooledthread() {
            super(threadpool.this,
                "pooledthread-" + (threadid++));
        }

        public void run() {
            while (!isinterrupted()) {

                // 得到任务
                runnable task = null;
                try {
                    task = gettask();
                }
                catch (interruptedexception ex) { }

                // 若gettask()返回null或中断，则关闭此线程并返回
                if (task == null) {
                    return;
                }

                // 运行任务，吸收异常
                try {
                    task.run();
                }
                catch (throwable t) {
                    uncaughtexception(this, t);
                }
            }
        }
    }
}
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要测试这个线程池，可以通过下面这个test程序！
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(threadpooltest.java)
public class threadpooltest {

    public static void main(string[] args) {
        if (args.length != 2) {
            system.out.println("tests the threadpool task.");
            system.out.println(
                "usage: java threadpooltest numtasks numthreads");
            system.out.println(
                "  numtasks - integer: number of task to run.");
            system.out.println(
                "  numthreads - integer: number of threads " +
                "in the thread pool.");
            return;
        }
        int numtasks = integer.parseint(args[0]);
        int numthreads = integer.parseint(args[1]);

        // 生成线程池
        threadpool threadpool = new threadpool(numthreads);

        // 运行任务
        for (int i=0; i<numtasks; i++) {
            threadpool.runtask(createtask(i));
        }

        // 关闭线程池并等待所有任务完成
        threadpool.join();
    }

    /**
        一个简单的任务(打印id)
    */
    private static runnable createtask(final int taskid) {
        return new runnable() {
            public void run() {
                system.out.println("task " + taskid + ": start");

                // 增加耗时
                try {
                    thread.sleep(500);
                }
                catch (interruptedexception ex) { }

                system.out.println("task " + taskid + ": end");
            }
        };
    }

}
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这样的线程池可以在许多地方应用！