OOPS in JAVA 12

OOPS in JAVA 12

Aggregation in Java

If a class have an entity reference, it is known as Aggregation. Aggregation represents HAS-A relationship.

Example:

class Employee{  
  int id;  
  String name;  
  Address address; //Address is a class  
  ...  
}

In such case, Employee has an entity reference address, so relationship is Employee HAS-A address.

Why use Aggregation??

For Code Reusability.

When use Aggregation??

1. Code reuse is also best achieved by aggregation when there is no IS-A relationship.

2. Inheritance should be used only if the relationship IS-A is maintained throughout the lifetime of the objects involved; otherwise, aggregation is the best choice.