JAVA多线程(二十三)Java多线程之ScheduledThreadPoolExecutor定时执行任务线程池

1.JAVA多线程(二十三)Java多线程之ScheduledThreadPoolExecutor定时执行任务线程池

1.1 定时执行任务线程池ScheduledThreadPoolExecutor

   ScheduledThreadPoolExecutor是一个使用线程池执行定时任务的类，相较于Java中提供的另一个执行定时任务的类Timer，其主要有如下两个优点：

• 使用多线程执行任务，不用担心任务执行时间过长而导致任务相互阻塞的情况，Timer是单线程执行的，因而会出现这个问题。
• 不用担心任务执行过程中，如果线程失活，其会新建线程执行任务，Timer类的单线程挂掉之后是不会重新创建线程执行后续任务的。

时cheduledThreadPoolExecutor定 执行任务线程池继承结构关系图：

通过源代码查看ScheduledThreadPoolExecutor构造函数实现：

    /**
     * 创建一个ScheduledThreadPoolExecutor，需要指定核心线程池大小。
     * Creates a new {@code ScheduledThreadPoolExecutor} with the
     * given core pool size.
     *
     * @param corePoolSize the number of threads to keep in the pool, even
     *        if they are idle, unless {@code allowCoreThreadTimeOut} is set
     * @throws IllegalArgumentException if {@code corePoolSize < 0}
     */
    public ScheduledThreadPoolExecutor(int corePoolSize) {
   
   
        super(corePoolSize, Integer.MAX_VALUE, 0, NANOSECONDS,
              new DelayedWorkQueue());
    }

    /**
     * Creates a new ScheduledThreadPoolExecutor with the given
     * initial parameters.
     *
     * @param corePoolSize the number of threads to keep in the pool, even
     *        if they are idle, unless {@code allowCoreThreadTimeOut} is set
     * @param handler the handler to use when execution is blocked
     *        because the thread bounds and queue capacities are reached
     * @throws IllegalArgumentException if {@code corePoolSize < 0}
     * @throws NullPointerException if {@code handler} is null
     */
    public ScheduledThreadPoolExecutor(int corePoolSize,
                                       RejectedExecutionHandler handler) {
   
   
        super(corePoolSize, Integer.MAX_VALUE, 0, NANOSECONDS,
              new DelayedWorkQueue(), handler);
    }

    /**
     * Creates a new {@code ScheduledThreadPoolExecutor} with the
     * given initial parameters.
     *
     * @param corePoolSize the number of threads to keep in the pool, even
     *        if they are idle, unless {@code allowCoreThreadTimeOut} is set
     * @param threadFactory the factory to use when the executor
     *        creates a new thread
     * @throws IllegalArgumentException if {@code corePoolSize < 0}
     * @throws NullPointerException if {@code threadFactory} is null
     */