Relationships between Classes
use
- A uses B: A calls a method (sends a message to) an object of class B or creates, receives, or returns an object of class B.
- containment
- A has a B: special case of use - an object of class A contains an object of B
inheritance
- B is an A: specialization - B extends A (is a subclass of A) if B has all the variables and methods of A (and more).
- In the class definition of B, the child class, there is no need to repeat declarations of variables and methods of A, they are assumed to be there. The definition of B has the additional variables and methods of B.