public ThreadPoolExecutor(int corePoolSize,
                          int maximumPoolSize,
                          long keepAliveTime,
                          TimeUnit unit,
                          BlockingQueue<Runnable> workQueue,
                          ThreadFactory threadFactory,
                          RejectedExecutionHandler handler) {
    //先判断参数是否合法
    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();
    //核心线程数量
    this.corePoolSize = corePoolSize;
    //最大线程数量
    this.maximumPoolSize = maximumPoolSize;
    //工作队列
    this.workQueue = workQueue;
    //保活时间，unit为时间单位，转换为秒
    this.keepAliveTime = unit.toNanos(keepAliveTime);、
    //线程工厂
    this.threadFactory = threadFactory;
    //拒绝策略
    this.handler = handler;
}