Association, Aggregation, Composition

I have a hand, I have a car.

I have a hand - life time of hand is same as my life time. hand dies with me :) it is tightly coupled. Its composition

I have a car - my car remains even if  I die. This is aggregation.

association: is a relationship between two classes. It is the basic way of relation between two classes.

aggregation and association are more specific way of relationship between classes.

aggregation: has a relationship. one class can exist without other class
composition: one class is tightly coupled with other class. Life time of the classes will be the same.

Example2:


university has a chancellor   (association)
university have faculties  (composition)


university can exist without chancellors
university cannot exist without faculties. if faculties dispose then university will not exist.

university composed of faculties