• 学习掌握声明和定义类及成员。

• 学习掌握访问类对象成员。

• 学习掌握保护数据如何屏蔽外部访问的原理，更好的认识类的封装-•　Learn to master classes and members of declarations and definitions.

•　learning and mastering a visit to a member of the class object.

•　learning to master how to protect data to shield external access principle, better understanding of the class package