线程池的简单实现

来源：互联网发布：iphone软件怎么做编辑：程序博客网时间：2024/04/23 21:19
public interface ThreadPool<Job extends Runnable> {    // 执行一个Job，这个Job需要实现Runnable    void execute(Job job);    // 关闭线程池    void shutdown();    // 增加工作者线程    void addWorkers(int num);    // 减少工作者线程    void removeWorker(int num);    // 得到正在等待执行的任务数量    int getJobSize();}线程池具体实现如下：public class DefaultThreadPool<Job extends Runnable> implements ThreadPool<Job> {    // 线程池最大限制数    private static final int MAX_WORKER_NUMBERS = 10;    // 线程池默认的数量    private static final int DEFAULT_WORKER_NUMBERS = 5;    // 线程池最小的数量    private static final int MIN_WORKER_NUMBERS = 1;    // 这是一个工作列表，将会向里面插入工作    private final LinkedList<Job> jobs = new LinkedList<Job>();    // 工作者列表    private final List<Worker> workers = Collections.synchronizedList(new ArrayList<Worker>());    // 工作者线程的数量    private int workerNum = DEFAULT_WORKER_NUMBERS;    // 线程编号生成    private AtomicLong threadNum = new AtomicLong();    public DefaultThreadPool()    {        initializeWokers(DEFAULT_WORKER_NUMBERS);    }    public DefaultThreadPool(int num)    {        workerNum = num > MAX_WORKER_NUMBERS ? MAX_WORKER_NUMBERS : num < MIN_WORKER_NUMBERS ? MIN_WORKER_NUMBERS : num;        initializeWokers(workerNum);    }    public void execute(Job job)    {        if (job != null)        {            // 添加一个工作，然后进行通知            synchronized (jobs)            {                jobs.addLast(job);                jobs.notify();            }        }    }    public void shutdown()    {        for (Worker worker : workers)        {            worker.shutdown();        }    }    public void addWorkers(int num)    {        synchronized (jobs)        {            // 限制新增的Worker数量不能超过最大值            if (num + this.workerNum > MAX_WORKER_NUMBERS)            {                num = MAX_WORKER_NUMBERS - this.workerNum;            }            initializeWokers(num);            this.workerNum += num;        }    }    public void removeWorker(int num)    {        synchronized (jobs)        {            if (num >= this.workerNum)            {                throw new IllegalArgumentException("beyond workNum");            }            // 按照给定的数量停止Worker            int count = 0;            while (count < num)            {                workers.get(count).shutdown();                count++;            }            this.workerNum -= count;        }    }    public int getJobSize()    {        return jobs.size();    }    // 初始化线程工作者    private void initializeWokers(int num)    {        for (int i = 0; i < num; i++)        {            Worker worker = new Worker();            workers.add(worker);            Thread thread = new Thread(worker, "ThreadPool-Worker-" + threadNum.incrementAndGet());            thread.start();        }    }    // 工作者，负责消费任务    class Worker implements Runnable    {        // 是否工作        private volatile boolean running = true;        public void run()        {            while (running)            {                Job job = null;                synchronized (jobs)                {                    // 如果工作者列表是空的，那么就wait                    while (jobs.isEmpty())                    {                        try                        {                            jobs.wait();                        }                        catch (InterruptedException ex)                        {                            // 感知到外部对WorkerThread的中断操作，返回                            Thread.currentThread().interrupt();                            return;                        }                    }                    // 取出一个Job                    job = jobs.removeFirst();                }                if (job != null)                {                    try                    {                        job.run();                    }                    catch (Exception ex)                    {                        // 忽略Job执行中的Exception                    }                }            }        }        public void shutdown()        {            running = false;        }    }}
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