A class diagram is a type of UML (Unified Modeling Language) diagram that represents the structure of a system by showing the classes of objects within it, their attributes, methods, and the relationships between them.
In a class diagram, classes are represented as boxes containing the class name and its attributes and methods. The attributes of a class represent the data or information that the class holds, while methods represent the operations that can be performed on that data.
The relationships between classes are shown as lines between the boxes, with different types of lines representing different types of relationships, such as inheritance, aggregation, or association.
Class diagrams are a useful tool for designing and documenting object-oriented systems, as they provide a clear and visual representation of the system’s structure and can help in identifying potential issues or areas for improvement.
In this example, we have three classes: Customer, Order, and Item.
The Customer class has two attributes: customerId and customerName. It also has two methods: placeOrder() and cancelOrder().
The Order class has three attributes: orderId, orderDate, and totalAmount. It also has two methods: addItem() and removeItem().
The Item class has two attributes: itemId and itemName.
The relationships between the classes are represented by the lines between the boxes. In this case, we have an association relationship between Customer and Order, as well as between Order and Item.
This class diagram shows that a Customer can place an Order, which can contain one or more Items. It also shows that an Order can be associated with only one Customer, and an Item can be associated with one or more