1．理解抽象类的概念，抽象类与普通类的区别

2．理解接口的概念，掌握接口的定义以及implements关键字的用法

3. 理解抽象类与接口的区别，体会抽象类与接口在解决实际问题时的区别

-1. Understand the concept of abstract classes, abstract classes and the difference between an ordinary class 2. Understand the concept of interface, control interface definition, and implements the use of keywords 3. To understand the difference between abstract classes and interfaces, abstract classes and interfaces experience solving practical problems in the difference between