线程池的状态

线程池的状态

private final AtomicInteger ctl = new AtomicInteger(ctlOf(RUNNING, 0));
这个 ctl 维护工作线程个数及线程池的状态，int32 位的数据类型，高3位维护线程状态，低29位维护工作线程对的数量

    private static final int COUNT_BITS = Integer.SIZE - 3;
    private static final int CAPACITY   = (1 << COUNT_BITS) - 1;

    // runState is stored in the high-order bits
    //创建线程了正常执行，
    private static final int RUNNING    = -1 << COUNT_BITS;
    //shutdown操作，停止接收execute提交过来的任务，正在处理的任务依然会执行，队列中的任务也会正常做完
    private static final int SHUTDOWN   =  0 << COUNT_BITS;
    
    //执行shutdownNow() ,进入stop 状态 ，正在处理的任务都会被中断，阻塞队列中的任务都不会被执行
    private static final int STOP       =  1 << COUNT_BITS;
    // 提供的过度状态，可自己实现
    private static final int TIDYING    =  2 << COUNT_BITS;
    // 线程池完全被销毁
    private static final int TERMINATED =  3 << COUNT_BITS;