Abstract class

 // Abstract class

abstract class Shape 

{

    double dim1, dim2;

    Shape(double a) 

{

        dim1 = a;

        dim2 = 0;

    }

Shape(double a, double b) 

{

        dim1 = a;

        dim2 = b;

    }

    // Abstract method

    abstract void printArea();

}

// Rectangle class

class Rectangle extends Shape 

{

    Rectangle(double length, double breadth) 

{

        super(length, breadth);

    }

    void printArea() 

{

        double area = dim1 * dim2;

        System.out.printf("Area of Rectangle = %.2f%n", area);

    }

}

// Triangle class

class Triangle extends Shape 

{

    Triangle(double base, double height) 

{

        super(base, height);

    }

    void printArea() 

{

        double area = 0.5 * dim1 * dim2;

        System.out.printf("Area of Triangle = %.2f%n", area);

    }

}

// Circle class

class Circle extends Shape 

{

    Circle(double radius) 

{

        super(radius);

    }

    void printArea() 

{

        double area = Math.PI * dim1 * dim1;

        System.out.printf("Area of Circle = %.2f%n", area);

    }

}

public class Demo_Abstract 

{

    public static void main(String as[]) 

{

        Rectangle r = new Rectangle(10, 5);

        r.printArea();

        Triangle t = new Triangle(6, 8);

        t.printArea();

        Circle c = new Circle(7);

        c.printArea();

    }

}