Aggregation in Java is a concept where one class contains a reference to another class, representing a HAS-A relationship. This relationship is a form of association where the contained objects can exist independently of the container object. Aggregation is used for code reusability and to model relationships between objects in a modular and reusable way¹².

Example of Aggregation

Consider a scenario where an Employee class contains an Address object. The Address class has its own attributes such as city, state, and country. This relationship can be represented as follows: