What is the Difference Between Class Diagram and Object Diagram?

The main difference between a class diagram and an object diagram lies in their purpose and the level of detail they illustrate. Here are the key differences:

Class Diagram:
Purpose: Represents the static structure of a software system, focusing on the relationships and structure of classes.
Elements: Typically includes classes, interfaces, abstract classes, associations, generalizations (inheritance), dependencies, and multiplicities.
Use Cases: Designing the overall architecture of a system, defining the classes and their relationships, and illustrating how different classes collaborate to achieve the system's functionality.
Example: In a class diagram, you might represent classes like "Car," "Engine," and "Wheel," showing their attributes and methods, as well as relationships like "Car has an Engine" and "Car has Wheels".
Object Diagram:
Purpose: Captures a snapshot of the runtime instances of classes and the relationships between them.
Elements: Focuses on objects and their relationships at a specific point in time.
Use Cases: Mainly to show examples of data structures and how objects in a system are interacting with each other at some point in time.
Example: An object diagram might show specific objects like "Engine1," "Wheel1," and "Car1," along with their attributes and relationships at a particular moment during the program's execution.

In summary, class diagrams serve as a foundational tool for representing the static structure of a software system, illustrating classes, their attributes, methods, and relationships. Object diagrams, on the other hand, focus on capturing specific instances of classes and their interactions at a particular point in time.