使用Java的Worker类进行后台任务处理

    private final class Worker
      extends AbstractQueuedSynchronizer
      implements Runnable{
        /**
         * This class will never be serialized, but we provide a
         * serialVersionUID to suppress a javac warning.
         */
        private static final long serialVersionUID = 6138294804551838833L;
 
        /** Thread this worker is running in.  Null if factory fails. */
       // 执行任务的线程
        final Thread thread;
        /** Initial task to run.  Possibly null. */
       // 执行的任务
        Runnable firstTask;
        /** Per-thread task counter */
        volatile long completedTasks;
 
        /**
         * Creates with given first task and thread from ThreadFactory.
         * @param firstTask the first task (null if none)
         */
        Worker(Runnable firstTask) {
          // 新建线程的时候，设置state -1 是为了防止线程还未执行时（线程只有在执行的时候才会被中断），就被     // 其它线程显式调用shutdown方法中断了，因为中断是要判断state大于等于0才会中断
          setState(-1);
          this.firstTask = firstTask;
          // 新建了一个线程
          this.thread = getThreadFactory().newThread(this);
        }
 
        /** Delegates main run loop to outer runWorker  */
        public void run() {
            runWorker(this);
        }