What is association, aggregation and composition in oops

Association
Association is a relationship where all object have their own lifecycle and there is no owner. Let’s take an example of Teacher and Student. Multiple students can associate with single teacher and single student can associate with multiple teachers but there is no ownership between the objects and both have their own lifecycle. Both can create and delete independently.
Points:
• Is a Relationship between objects.
• Objects have independent lifecycles.
• There is no owner.
• Objects can create and delete independently.

Aggregation
Aggregation is a specialize form of Association where all object have their own lifecycle but there is ownership and child object can not belongs to another parent object. Let’s take an example of Department and teacher. A single teacher can not belongs to multiple departments, but if we delete the department teacher object will not destroy. We can think about “has-a” relationship.
Points:
• Specialize form of Association.
• has-a relationship between objects
• Object have independent life-cycles
• Parent-Child relationship
Composition
Composition is again specialize form of Aggregation. It is a strong type of Aggregation. Child object dose not have their lifecycle and if parent object deletes all child object will also be deleted. Let’s take again an example of relationship between House and rooms. House can contain multiple rooms there is no independent life of room and any room can not belongs to two different house if we delete the house room will automatically delete. Let’s take another example relationship between Questions and options. Single questions can have multiple options and option can not belong to multiple questions. If we delete questions options will automatically delete.
Points:
• Specialize form of Aggregation
• Strong Type of Aggregation.
• Parent-Child relationship
• Only parent object has independent life-cycle.