// 初始值 -536870912
    private final AtomicInteger ctl = new AtomicInteger(ctlOf(RUNNING, 0));
    // 初始值 29
    private static final int COUNT_BITS = Integer.SIZE - 3;
    // 初始值 536870911
    private static final int CAPACITY   = (1 << COUNT_BITS) - 1;
    // RUNNING状态：接受新任务并处理排队任务
    private static final int RUNNING    = -1 << COUNT_BITS;
    // SHUTDOWN状态：不接受新任务，但处理排队任务
    private static final int SHUTDOWN   =  0 << COUNT_BITS;
    // STOP状态：不接受新任务，不处理排队任务，并中断正在进行的任务
    private static final int STOP       =  1 << COUNT_BITS;
    // All tasks have terminated, workerCount is zero,  the thread transitioning to state TIDYING will run the terminated() hook method
    private static final int TIDYING    =  2 << COUNT_BITS;
    // TERMINATED: terminated() has completed
    private static final int TERMINATED =  3 << COUNT_BITS;
    // 获取线程池状态，取前三位
    private static int runStateOf(int c)     { return c & ~CAPACITY; }
    // 获取当前正在工作的worker,主要是取后面29位
    private static int workerCountOf(int c)  { return c & CAPACITY; }
    // 生成ctl
    private static int ctlOf(int rs, int wc) { return rs | wc; }

/**
    * 单个创建核心线程
    */
    public boolean prestartCoreThread() {
        return workerCountOf(ctl.get()) < corePoolSize &&
            addWorker(null, true);
    }
    /**
    * 启动所有核心线程
    */
    public int prestartAllCoreThreads() {
        int n = 0;
        // 添加工作线程
        while (addWorker(null, true))
            ++n;
        return n;
    }    

private boolean addWorker(Runnable firstTask, boolean core) {
        retry:
        for (;;) {
            int c = ctl.get();
            // 获取运行状态
            int rs = runStateOf(c);
            /**
             * 如果当前的线程池的状态>SHUTDOWN 那么拒绝Worker的add 如果=SHUTDOWN
             * 那么此时不能新加入不为null的Task，如果在WorkCount为empty的时候不能加入任何类型的Worker，
             * 如果不为empty可以加入task为null的Worker,增加消费的Worker
             */
            if (rs >= SHUTDOWN &&
                    ! (rs == SHUTDOWN &&
                            firstTask == null &&
                            ! workQueue.isEmpty()))
                return false;


            for (;;) {
                // 获取有效线程数，并判断//如果当前的数量超过了CAPACITY，或者超过了corePoolSize和maximumPoolSize（试core而定），则直接返回
                int wc = workerCountOf(c);
                if (wc >= CAPACITY ||
                        wc >= (core ? corePoolSize : maximumPoolSize))
                    return false;
                // //CAS尝试增加线程数，如果失败，证明有竞争，那么重新到retry。
                if (compareAndIncrementWorkerCount(c))
                    break retry;
                c = ctl.get();  // Re-read ctl
                // 继续判断当前线程池的运行状态
                if (runStateOf(c) != rs)
                    continue retry;
                // else CAS failed due to workerCount change; retry inner loop
            }
        }

        /**
         * 新建任务
         */
        Worker w = new Worker(firstTask);
        Thread t = w.thread;

        final ReentrantLock mainLock = this.mainLock;
        mainLock.lock();
        try {
            // Recheck while holding lock.
            // Back out on ThreadFactory failure or if
            // shut down before lock acquired.
            int c = ctl.get();
            int rs = runStateOf(c);
            /**
             * rs!=SHUTDOWN ||firstTask!=null
             *
             * 同样检测当rs>SHUTDOWN时直接拒绝减小Wc，同时Terminate，如果为SHUTDOWN同时firstTask不为null的时候也要Terminate
             */
            if (t == null ||
                    (rs >= SHUTDOWN &&
                            ! (rs == SHUTDOWN &&
                                    firstTask == null))) {
                decrementWorkerCount();
                tryTerminate();
                return false;
            }

            workers.add(w);

            int s = workers.size();
            if (s > largestPoolSize)
                largestPoolSize = s;
        } finally {
            mainLock.unlock();
        }

        t.start();
        //Stop或线程Interrupt的时候要中止所有的运行的Worker
        if (runStateOf(ctl.get()) == STOP && ! t.isInterrupted())
            t.interrupt();
        return true;
    }