What is the Difference Between Association and Aggregation?

The main difference between association and aggregation lies in the nature of the relationship between the classes involved. Here are the key differences:

• Association: Association refers to a relationship between two classes that use each other, represented by a "has a" relationship. It is a more general relationship and can be unidirectional or bidirectional. For example, a student has a teacher, and a teacher has multiple students.
• Aggregation: Aggregation is a special type of association that specifies a whole-part relationship, where one class contains a collection of objects of another class. It is more specific and inflexible in nature. In aggregation, the parts can exist independently of the whole, and the relationship is represented by a "has a+" relationship. For example, a department has multiple employees, with employees being the parts and the department being the whole.

In summary, association represents a more general relationship between classes, while aggregation is a specific type of association that specifies a whole-part relationship.

Comparative Table: Association vs Aggregation

Here is a table comparing the differences between association and aggregation:

In summary, association is a relationship between two classes where one class uses another, and there is no ownership between the objects. On the other hand, aggregation is a special type of association that specifies a "has a" relationship, representing a collection or gathering of things together. In aggregation, there is ownership between two objects, and objects do not have their own lifecycle.