通过java中继承和组合的简单方法，修改字符串，可实现谁在干什么。也可在类内通过增加方法，在已有框架下实现多种继承和组合-Java inheritance and composition by the simple method, modify the string, can be realized who was doing. Can also be within the class by adding methods to achieve the existing framework of the combination of multiple inheritance and