1.　　设计2-3个具体的货物类（如书本类Book，食品类Food等）继承自货物类Item，增加成员变量和成员方法，重写父类已有的方法printItemInfo()

2.　　1)设计结算接口SettleAccount，定义方法getAccount()；

2) 设计SettleAccount接口实现类Customer和Member。Customer为普通顾客类，结算金额为购物车价格总计+配送费8元；Member为会员类，结算金额为购物车价格总计的7折，无需配送费。

3) 设计订单类Order，定义购物车类Cart对象，SettleAccount接口变量，其成员方法包括：构造函数，set和get方法，打印订单信息方法printOrderInfo()来输出购物车信息和结算金额

3.　　在主方法中实现：

1)　　定义2个订单类Order对象，普通顾客订单order1和会员订单order2，初始化变量

2)　　分别对购物车添加若干购物车物品，并打印订单信息

3)　　分别修改某一购物车物品的数量，并打印订单信息

4)　　分别对购物车删除若干购物车物品，并打印订单信息

-1. Design 2-3 specific goods (such as books class Book, Food Food, etc.) inherited　the cargo class Item, increase member variables and member methods, override the parent class has a method printItemInfo () 2. 1) Design settlement Interface SettleAccount, define methods getAccount ()　2) design SettleAccount interface class Customer and Member. Customer as an ordinary customer class, the settlement amount of shopping cart price Total+ Shipment eight yuan　Member of the class members, the settlement amounted to cart price totaled 7 , no delivery fee. 3) design wins Class Order, define the class Cart Shopping Cart objects, SettleAccount interface variables, its members comprising: a constructor, set and get methods, print order information methods printOrderInfo () to output the shopping cart information and 3. In the main settlement amount Methods to achieve: 1) Define two orders Order object classes, and members of the general customer orders order1 orders order2, initialize variables