用双向链表实现的一个任务队列，把自己定义的任务继承基类BaseQueue，可以实现对任务的增加，删除，优先级的设置，获取任务等等。-With a doubly linked list to achieve a task queue , put their defined tasks inherit the base class BaseQueue, can be added to the task , delete, priority setting , access to the task a