什么是线程池？

最新推荐文章于 2025-06-16 23:02:40 发布

BaryLeo

最新推荐文章于 2025-06-16 23:02:40 发布

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分类专栏：笔记

本文链接：https://blog.youkuaiyun.com/weixin_41878312/article/details/113821968

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1.特点

线程池是一个三级存储结构，线程先放入核心线程池，满了之后放到缓存队列当中，最后如果缓存队列也满了则扩容新线程。
实现原理

2.1 构造方法

public ThreadPoolExecutor(int corePoolSize,
                          int maximumPoolSize,
                          long keepAliveTime,
                          TimeUnit unit,
                          BlockingQueue<Runnable> workQueue,
                          RejectedExecutionHandler handler) {
    this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
         Executors.defaultThreadFactory(), handler);
}

添加worker线程一直执行run，去workQueue获取任务并执行；blockQueue的take方法是阻塞的，若队列为空，则挂起；挂起超过一定时间，就销毁线程。

3. 接口

Executor
ExecutorService

4. 自定义线程池

public ThreadPoolExecutor(int corePoolSize,
                          int maximumPoolSize,
                          long keepAliveTime,
                          TimeUnit unit,
                          BlockingQueue<Runnable> workQueue,
                          ThreadFactory threadFactory,
                          RejectedExecutionHandler handler) {
    if (corePoolSize < 0 ||
        maximumPoolSize <= 0 ||
        maximumPoolSize < corePoolSize ||
        keepAliveTime < 0)
        throw new IllegalArgumentException();
    if (workQueue == null || threadFactory == null || handler == null)
        throw new NullPointerException();
    this.acc = System.getSecurityManager() == null ?
            null :
            AccessController.getContext();
    this.corePoolSize = corePoolSize;
    this.maximumPoolSize = maximumPoolSize;
    this.workQueue = workQueue;
    this.keepAliveTime = unit.toNanos(keepAliveTime);
    this.threadFactory = threadFactory;
    this.handler = handler;
}