Basic HTML version of Foils prepared Sept 6 1998

Foil 25 Relationships between Classes

From Java Tutorial 98-2: Java Language and Object Oriented Techniques CPS606 Fall Semester 1999 -- Sept 7 1999. by Geoffrey C. Fox, Nancy McCracken
Account child class definition examples for Foil 25
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.

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