Develop a class diagram for a Message class for a cell phone company. Include generalizations for child
classes TextMessage, VideoMessage, and VoiceMessage.
The Message class has attributes of account number and price. In addition it has the methods
getInfo(accountNum) and calcPrice().
The subclasses each have one additional attribute of thier own. TextMessage has characterLength,
VideoMessage has messSize and VoiceMessage has numMinutes.
Each subclass overrides the methods of the superclass with thier own. No getter or setter methods need to
be documented.
The message class will have a constructor that takes the account number as an argument. Each subclass should also have their own constructor which takes their respective additional attribute as an argument; as well as the account number, obviously.
To develop a class diagram for the Message class and its subclasses, we need to consider the attributes, methods, and relationships between the classes. Here's a step-by-step guide on how to create the class diagram:
1. Start by creating a box for the Message class in the center of your diagram.
2. Inside the box, list the attributes accountNumber and price.
3. Below the attributes, list the methods getInfo(accountNum) and calcPrice() inside another box.
4. Draw a line with an arrow pointing to the TextMessage class and label it "<<generalization>>".
5. Inside the TextMessage class, add the additional attribute characterLength.
6. Below the attribute, list the methods getInfo(accountNum) and calcPrice() inside another box. Make sure to indicate that these methods override the ones from the Message class.
7. Repeat steps 4-6 for the VideoMessage and VoiceMessage classes. The VideoMessage class should have the additional attribute messSize, and the VoiceMessage class should have the additional attribute numMinutes.
8. Connect the TextMessage class to the Message class with a line labeled "<<inheritance>>". Repeat this step for the VideoMessage and VoiceMessage classes as well.
Your class diagram for the Message class and its subclasses should look something like this:
```
+----------------------------------+
| Message |
+----------------------------------+
| -accountNumber: int |
| -price: double |
+----------------------------------+
| +getInfo(accountNum): void |
| +calcPrice(): double |
+----------------------------------+
^
|
+-------|--------------------------+
| V |
| TextMessage |
+----------------------------------+
| -characterLength: int |
+----------------------------------+
| +getInfo(accountNum): void |
| +calcPrice(): double |
+----------------------------------+
^
|
+-------|--------------------------+
| V |
| VideoMessage |
+----------------------------------+
| -messSize: int |
+----------------------------------+
| +getInfo(accountNum): void |
| +calcPrice(): double |
+----------------------------------+
^
|
+-------|--------------------------+
| V |
| VoiceMessage |
+----------------------------------+
| -numMinutes: int |
+----------------------------------+
| +getInfo(accountNum): void |
| +calcPrice(): double |
+----------------------------------+
```
Note that the attributes and methods that are inherited from the Message class are marked as private (-) and the ones added by each subclass are marked as private (+). The `<<inheritance>>` relationship indicates that the subclasses inherit from the Message class, and the `<<generalization>>` relationship shows the more specialized relationship between the subclasses and the Message class.