Introduction - If you have any usage issues, please Google them yourself
A statement both interfaces, Show and Print, in order to achieve multiple inheritance through interface implementation. Category as a class userInformation structure extends the parent class, one of the definition of f methods, g and showOut methods, implementation methods, respectively, inheritance, overloading, rewrite. Construction category telephoneCardUser, and extends userInformation through such implements Show, Print two interfaces to achieve the purpose of this experiment.