Example of Class Inheritance

Here is an example of how inheritance works in JAVA:

public class Rectangle {        

        // define instance variables:

        protected double width, height;

        public Rectangle (double w, double h )

                     width = w;

            height = h;

        public double calcArea()

return width * height;

        public double calcPerimeter()

             return 2 * (width + height);   }  

public class Square extends Rectangle {      

        public Square(double side 
                super(side, side); }

Class Square is derived from a base class Rectangle. Thus, public variables and methods of Rectangle are inherited in Square class. Notice the use of keyword ‘extends’ to derive a child class (Square) from a parent class (Rectangle).