Association Aggregation and Composition in Java

By | June 17, 2022

Association, aggregation, and composition are three types of relationships that can exist between objects in Java.

  1. Association: It is a relationship between two or more objects where they are connected but not dependent on each other. This means that one object can exist without the other, but they can still interact with each other. For example, a car object can be associated with a driver object, but the driver can still exist without the car.
  2. Aggregation: It is a special type of association where one object is composed of multiple other objects, and these objects can exist independently of each other. This means that the aggregated objects are not owned by the main object and can be shared with other objects. For example, a university object can aggregate multiple department objects, and these departments can be shared with other universities.
  3. Composition: It is a strong form of aggregation where one object owns and controls the lifetime of another object. This means that the composed objects cannot exist without the main object and are destroyed when the main object is destroyed. For example, a house object can compose multiple room objects, and these rooms cannot exist without the house.

In Java, these relationships can be implemented using instance variables, constructors, and methods. For example, a car object can have an instance variable for a driver object, and a university object can have an instance variable for an array of department objects. The relationship between objects can also be defined using UML diagrams, which provide a graphical representation of the objects and their relationships. Understanding these concepts is important for creating well-designed, maintainable, and scalable Java applications.

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That’s all about Association Aggregation and Composition in Java

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