Sams Teach Yourself Java™ in 24 Hours, Sixth Edition

Creating a Subclass

To see an example of inheritance at work, in the next project you create a class called Point3D that represents a point in three-dimensional space. You can express a two-dimensional point with an (x,y) coordinate. Applets use an (x,y) coordinate system to determine where text and graphics should be displayed. Three-dimensional space adds a third coordinate, which can be called z.

The Point3D class of objects should do three things:

• Keep track of an object’s (x,y,z) coordinate

• Move an object to a new (x,y,z) coordinate when needed

• Move an object by a certain amount of x, y, and z values as needed

Java already has a standard class that represents two-dimensional points; it’s called Point.

It has two integer variables called ...