1.Previous
3.Next

class Car are composed of four instances of the class Wheel. This particular implementation of Wheel is specific to a car, so the code does not model the general notion of a wheel that would be better represented as a top-level class. Therefore, it is semantically connected to the class Car and the code of Wheel is in some way coupled to its outer class, being a composition unit of a car. The wheel for a particular car is unique to that car, but for generalization, the wheel is

1.Previous
3.Next