Case Study: Point, Circle, Cylinder

• In this example, Circle inherits from Point, and Cylinder inherits from Circle.

Point

• Point's instance variables are protected.

  This allows Circle to directly access Point's instance variables (although it doesn't).

The Test applet must use Point's get methods.

Circle

• The Point class is reused here, but not shown.
• Since Circle extends Point, it inherits all of Point's non-private methods and instance variables (in this case, all of them).
• It then adds a double called radius, and several methods particular to Circle.
• It overrides Point's toString method, but invokes it via super.

Cylinder

• Point and Circle are reused, but not shown.
• Cylinder inherits all of Circle's non-private members (all of them).
• It adds a double called height, and corresponding get and set methods.
• It overrides Circle's area and toString methods.
• It adds a volume method.