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Object-oriented Programming in C#
Specialization, Extension, and Inheritance
An example of simple extension

We extend the 2D Point class to a 3D Point class

/user/normark/oop-csharp-1/sources/c-sharp/point/2d3d/Point.csThe class Point2D.

/user/normark/oop-csharp-1/sources/c-sharp/point/2d3d/Point3D.csThe class Point3D which extends class Point3d.

/user/normark/oop-csharp-1/sources/c-sharp/point/2d3d/Client.csA client of the classes Point2D and Point3d.

/user/normark/oop-csharp-1/sources/c-sharp/point/2d3d/outputThe output from the Client program.

Go to exercisePoint3D: A client or a subclass of Point2D?
  • Some observations:

    • A 3D point is not a 2D point

    • Thus, Point3D is not a specialization of Point2D

    • The set of 2D point objects is disjoint from the set of 3D points

The class Point2D was a convenient starting point of the class Point3D

We have reused some data and operations from class Point2D in class Point3D