Question

You have been asked to develop a mobile phone application that allows users to inventory items in their home for insurance purposes (in case of theft or fire.) Users can create categories and subcategories of items (Electronics, Computers, Furniture, etc.) and then list items within each category.

The software should allow the user to create a description of the item, take a photo, and input the purchase price. Other information may be required of specific types of objects (a TV would have a serial number, for example, while a sofa probably would not.)

Users can also list the rooms in their home and note the location of each item. From the above software description, please answer ALL of the following:

1. List three candidate classes that you believe would support this software

2. Describe at least one superclass-subclass relationship between two classes

3. Referring to your defined superclass-subclass relationship, list two attributes that would belong to the superclass and two attributes that would belong to the subclass.

Answer 1

Firstly we will break the problem in subpart:

• There is a user who can use the android Application.But we wont be having just a single person using the application.There will be multiple people using the application for the same purpose but will be having different credentials like name , password,contact number ,etc.So we can create a class User as classes are blueprints for the objects in the class.
• Secondly there are Items. Item can be a class in the same ways and can have common attributes as policy intact to the insurance,etc.They will differ in attribute values like id,pic ,etc. So the second class is "Item".
• Thirdly, we can have various types of item belonging to various categories and difference in attributes.An example of TV having a serial number and sofa don't having one.The classes could be "Electronic_Item","Furniture",etc.There can be many classes depending upon that.
• Now As classes Electronic_Item, Furniture ,etc are still type for an Item, they can extend common properties like id,Picture,Price,etc which will be same as of the class Item.They can have unique properties of there own like "Electronic_Item" can have serial_number as its attribute ,while Furniture can skip that property and can have "Made_Of" (for it being of wood,steel ,etc).

Now lets answer the questions :

1. 3 candidate classes can be : User,Item,Electronic_Item(though you can write more of them as explained above).
2. Superclass can be Item,subclasses can be Electronic_Item class ,Furniture class etc.An Electronic_Item class or Furniture class has an 'is a' relationship with its superclass Item.The subclasses can be considered special kind of its superclass.
3. Superclass "Item" would have attributes like : Item_name,Price,etc as all the Item instances will have some name like "TV" or "sofa" and a certain price which the user updates irrespective of its kind means whether its electronics or furniture. As of subclass "Electronic_Item class" can have serial number as its attribute whereas Furniture can have "made_of " as an attribute.