What is aggregation in Java?

Aggregation is a special form of association. It is also a relationship between two classes like association, however its a directional association, which means it is strictly a one way association. It represents a Has-A relationship. For example consider two classes Student class and Address class. read more

Aggregation in Java. If a class have an entity reference, it is known as Aggregation. Aggregation represents HAS-A relationship. Consider a situation, Employee object contains many informations such as id, name, emailId etc. read more

Aggregation in Java is a relationship between two classes that is best described as a "has-a" and "whole/part" relationship. It is a more specialized version of the association relationship. The aggregate class contains a reference to another class and is said to have ownership of that class. read more

The difference is that any composition is an aggregation and not vice versa. Let's set the terms. The Aggregation is a metaterm in the UML standard, and means BOTH composition and shared aggregation, simply named shared. Too often it is named incorrectly "aggregation". It is BAD, for composition is an aggregation, too. read more