ThreadPoolExecutor的构造函数

/**
 * Creates a new {@code ThreadPoolExecutor} 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 maximumPoolSize the maximum number of threads to allow in the
 *        pool
 * @param keepAliveTime when the number of threads is greater than
 *        the core, this is the maximum time that excess idle threads
 *        will wait for new tasks before terminating.
 * @param unit the time unit for the {@code keepAliveTime} argument
 * @param workQueue the queue to use for holding tasks before they are
 *        executed.  This queue will hold only the {@code Runnable}
 *        tasks submitted by the {@code execute} method.
 * @param threadFactory the factory to use when the executor
 *        creates a new thread
 * @param handler the handler to use when execution is blocked
 *        because the thread bounds and queue capacities are reached
 * @throws IllegalArgumentException if one of the following holds:<br>
 *         {@code corePoolSize < 0}<br>
 *         {@code keepAliveTime < 0}<br>
 *         {@code maximumPoolSize <= 0}<br>
 *         {@code maximumPoolSize < corePoolSize}
 * @throws NullPointerException if {@code workQueue}
 *         or {@code threadFactory} or {@code handler} is null
 */
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;
}

各个参数详细解释：
corePoolSize（线程池基本大小）：当向线程池提交一个任务时，若线程池已创建的线程数小于corePoolSize，
    即便此时存在空闲线程，也会通过创建一个新线程来执行该任务，直到已创建的线程数大于或等于corePoolSize时，才会根据是否存在空闲线程，来决定是否需要创建新的线程。除了利用提交新任务来创建和启动线程（按需构造），
也可以通过 prestartCoreThread() 或 prestartAllCoreThreads() 方法来提前启动线程池中的基本线程。
maximumPoolSize（线程池最大大小）：线程池所允许的最大线程个数。当队列满了，且已创建的线程数小于maximumPoolSize，则线程池会创建新的线程来执行任务。另外，对于无界队列，可忽略该参数。
keepAliveTime（线程存活保持时间）：默认情况下，当线程池的线程个数多于corePoolSize时，线程的空闲时间超过keepAliveTime则会终止。但只要keepAliveTime大于0，allowCoreThreadTimeOut(boolean) 
方法也可将此超时策略应用于核心线程。另外，也可以使用setKeepAliveTime()动态地更改参数。
unit（存活时间的单位）：时间单位，分为7类，从细到粗顺序：NANOSECONDS（纳秒），MICROSECONDS（微妙），MILLISECONDS（毫秒），SECONDS（秒），MINUTES（分），HOURS（小时），DAYS（天）；
workQueue（任务队列）：用于传输和保存等待执行任务的阻塞队列。可以使用此队列与线程池进行交互：
threadFactory（线程工厂）：用于创建新线程。由同一个threadFactory创建的线程，属于同一个ThreadGroup，创建的线程优先级都为Thread.NORM_PRIORITY，以及是非守护进程状态。threadFactory
创建的线程也是采用new Thread()方式，threadFactory创建的线程名都具有统一的风格：pool-m-thread-n（m为线程池的编号，n为线程池内的线程编号）；
handler（线程饱和策略）：当线程池和队列都满了，则表明该线程池已达饱和状态。