Use Cases

A use case is a description of a sequence of actions that a user can take to achieve a goal. Use cases are used to capture the functional requirements of a system. They are typically written in a natural language that is easy for stakeholders to understand.

The purpose of a use case is to:

• Identify the different ways that users will interact with the system.
• Document the functional requirements of the system.
• Communicate the functional requirements of the system to stakeholders.

Use cases play an important role in object-oriented-programming design by helping to identify the different classes that will be needed in the system. For example, if a use case describes a user buying a car, then the system will need classes to represent cars, customers, and salespeople.

Class Diagrams

A class diagram is a graphical representation of the classes in a system and their relationships to each other. Class diagrams are used to capture the structural requirements of a system. They are typically written in a notation that is specific to object-oriented programming.

The purpose of a class diagram is to:

• Identify the different classes in the system.
• Document the relationships between classes.
• Communicate the structural requirements of the system to stakeholders.

Class diagrams play an important role in object-oriented-programming design by helping to visualize the structure of the system. For example, a class diagram for an automobile dealership might show classes for cars, customers, salespeople, and orders.

Class Diagram for an Automobile Dealership

Here is a class diagram for an automobile dealership:

class Car {
  String make;
  String model;
  int year;
  int mileage;
  double price;
}

class Customer {
  String name;
  String address;
  String phone;
  String email;
}

class Salesperson {
  String name;
  String licenseNumber;
  int yearsOfExperience;
}

class Order {
  Car car;
  Customer customer;
  Salesperson salesperson;
  Date purchaseDate;
  double price;
}

Car <-- Order
Customer <-- Order
Salesperson <-- Order

This class diagram shows six classes: Car, Customer, Salesperson, Order, Make, and Model. The relationships between the classes are shown with arrows. For example, the arrow from Car to Order shows that a Car can be ordered by a Customer.

This class diagram is a simplified representation of an automobile dealership. It does not show all of the classes and relationships that would be needed in a real-world dealership. However, it is enough to illustrate the basic concepts of class diagrams and their use in object-oriented-programming design.