Hi everyone
I am new to OOA and OOD and in UML.I must clarify these concepts in my mind.
-Association
-Composition
-Aggregation
-Dependancy
-Is Association a superset of Aggregation and Composition?
Can anybode give me any links or examples how these are implemented in Java?
> -Association
One class knows about the existence of another and may address it directly by it's name.
> -Composition
Composition is a specialisation of an Association with a lifetime constraint. It means that once class is made up with one of more other classes. A Car is a composite of a Body, an Engine, a Gearbox, etc. The lifetime of all, and coupling is implicitly the same. e.g. Without these it is not really a car. This is sometimes said to be a static relationship.
> -Aggregation
Composition is a specialisation of an Association without a lifetime constraint. It is a much more dynamic relationship. One class is a container for other classes, the other classes may be added or removed from the container as required. The lifetime of each is independent. e.g. A Car's relationship to a driver & passengers.
> -Dependancy
Dependency is an artifact of compile or link time interface resolution and checking. A change to the interface of dependancy target will result in a change to the depemdant.
> -Is Association a superset of Aggregation and Composition?
Yes.
> Can anybode give me any links or examples how these
> are implemented in Java?
I suggest you download a trial or free UML tool, and try them for yourself. Try different relationships, different multiplicity and examine the generated code.
