Name and describe the three common class relationships.
- Dependency: a class method has another class type
as a parameter or return value, or it constructs an object of another class
(a class "uses" another class)
- Aggregation (or Association): a class has an
instance variable that is another class type or a collection of another
class type (a class object "has" an object of another class type as part of
its state)
- Inheritance: a class is a subclass of another (an object that is an
instance of one class "is" also an instance of another)