Aggregation is a specific type of association in object-oriented programming that represents a "has-a" relationship between two classes. It is often described as a whole-part relationship, where the whole can contain multiple parts, but the parts can exist independently of the whole. This is a key distinction from composition, which is a stronger form of association where the parts cannot exist without the whole.

Code Example

In Java, aggregation can be implemented by having one class contain a reference to another. Here's a simple example to illustrate aggregation between a Department class and a Student class: