7. Polymorphism

Polymorphism stands for uniform interface .

Each derived class inherits the base interface.

Each derived class provides its own implementation of each method in the interface.

When uniform message (like draw) is sent to an object, it will respond in a distinct way.

Shape Java class:

public abstract class Shape {
    private double area;
    public abstract double getArea();
}

Shape UML diagram:

Rectangle Java class:

public class Rectangle extends Shape{
    double length;
    double width;

    public Rectangle( double l, double w ) {
        length = l;
        width = w;
    }

    public double getArea() {
        area = length * width;
        return ( area );
    }
}

Circle Java class:

public class Circle extends Shape {
    double radius;

    public Circle( double r ) {
        radius = r;
    }

    public double getArea() {
        area = 3.14 * ( radius * radius );
        return ( area );
    }
}