Abstract Learn

package AbstractClass2;

public class Circle extends Shape{
    Circle(double a)
    {
        super(a,a);
    }
   void area()
    {
        double result=3.1416*a*a;
        System.out.println("Result is: "+result);

    }
}

package AbstractClass2;

public class Rectangle extends Shape{
    Rectangle(double a, double b)
    {
        super(a,b);
    }

    @Override
   void area() {
        double result=a*b;
        System.out.println("Result is: "+result);
    }
}

package AbstractClass2;

public abstract class Shape {
    double a,b;
    Shape(double a, double b)
    {
        this.a=a;
        this.b=b;
    }

 abstract void area();


}
package AbstractClass2;

public class Triangle extends Shape {
    Triangle(double a, double b)
    {
        super(a,b);
    }

    @Override
 void area() {
        double result= .5*a*b;
        System.out.println("Result is: "+result);
    }
}

package AbstractClass2;

import java.util.Scanner;

public class Test {
    public static void main(String[] args) {
        Scanner sc =new Scanner(System.in);
        Shape shape;
        shape =new Triangle(sc.nextDouble(),sc.nextDouble());
        shape.area();
        shape =new Rectangle(sc.nextDouble(),sc.nextDouble());
        shape.area();
        shape =new Circle(sc.nextDouble());
        shape.area();
    }
}