private boolean addWorker(Runnable firstTask, boolean core) {
        retry:
	//死迴圈更新狀態
        for (;;) {
            int c = ctl.get();
            int rs = runStateOf(c);//獲取執行狀態

	    //檢查執行緒池是否處於關閉狀態
            if (rs >= SHUTDOWN &&
                ! (rs == SHUTDOWN &&
                   firstTask == null &&
                   ! workQueue.isEmpty()))
                return false;
	
            for (;;) {
		  //獲取當前工作執行緒數量
                int wc = workerCountOf(c);
		//如果已經超過corePoolSize獲取maximumPoolSize 返回false
                if (wc >= CAPACITY ||
                    wc >= (core ? corePoolSize : maximumPoolSize))
                    return false;
		//CAS增加一個工作執行緒
                if (compareAndIncrementWorkerCount(c))
                 break retry;
		//再次獲取狀態
                c = ctl.get();  // Re-read ctl
		//如果狀態更新失敗 則迴圈更新
                if (runStateOf(c) != rs)
                    continue retry;
                // else CAS failed due to workerCount change; retry inner loop
            }
        }

        boolean workerStarted = false;
        boolean workerAdded = false;
        Worker w = null;
        try {
            w = new Worker(firstTask);//初始化一個工作執行緒
            final Thread t = w.thread;
            if (t != null) {
		 //獲得鎖
                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 rs = runStateOf(ctl.get());

                    if (rs < SHUTDOWN ||
                        (rs == SHUTDOWN && firstTask == null)) {
                        if (t.isAlive()) // precheck that t is startable
                            throw new IllegalThreadStateException();
			//新增工作這到hashset中儲存
                        workers.add(w);
                        int s = workers.size();
                        if (s > largestPoolSize)
                            largestPoolSize = s;
                        workerAdded = true;
                    }
                } finally {
                    mainLock.unlock();
                }
                if (workerAdded) {
		//工作執行緒啟動 執行第一個任務 就是新提交的任務
                    t.start();
                    workerStarted = true;
                }
            }
        } finally {
            if (! workerStarted)
                addWorkerFailed(w);
        }
        return workerStarted;
    }