We have to calculate the area of a rectangle, a square and a circle. Create an abstract class "Shape" with three abstract methods namely "RectangleArea"; taking two parameters, "SquareArea" and "CircleArea" taking one parameter each. The parameters of "RectangleArea" are its length and breadth, that of "SquareArea" is its side and that of "CircleArea" is its radius. Now create another class "Area" containing all the three methods "RectangleArea", "SquareArea" and "CircleArea" for printing the area of rectangle, square and circle respectively. Create an object of class "Area" and call all the three methods.

Here are some additional points to consider before writing the code:

In Java, we use the abstract keyword to define abstract classes and methods. Abstract methods have no implementation and are defined without braces and followed by a semicolon.

An abstract class cannot be instantiated, which means we cannot create an object of an abstract class. We can only create objects of its concrete subclasses.

A concrete class is a regular class that provides the implementation details for all the abstract methods inherited from its abstract superclass.

In Java, we use the @Override annotation to indicate that a method is intended to override a method in the superclass. This is optional but recommended to avoid accidental overloading.

 

Keeping these points in mind, we can now proceed with writing the code.

Source Code..

Here is the implementation of the code:

 

import java.lang.Math;

 

abstract class Shape {

    public abstract void RectangleArea(int length, int breadth);

    public abstract void SquareArea(int side);

    public abstract void CircleArea(int radius);

}

 

class Area extends Shape {

   

    @Override

    public void RectangleArea(int length, int breadth) {

        int area = length * breadth;

        System.out.println("Area of Rectangle: " + area);

    }

   

    @Override

    public void SquareArea(int side) {

        int area = side * side;

        System.out.println("Area of Square: " + area);

    }

   

    @Override

    public void CircleArea(int radius) {

        double area = Math.PI * radius * radius;

        System.out.println("Area of Circle: " + area);

    }

}

 

public class Main {

    public static void main(String[] args) {

        Area areaObj = new Area();

        areaObj.RectangleArea(10, 20);

        areaObj.SquareArea(15);

        areaObj.CircleArea(5);

    }

}

Code Explanation:

In this code, we have defined an abstract class Shape with three abstract methods RectangleArea, SquareArea, and CircleArea. We have also defined a concrete class Area that extends the Shape class and provides the implementation details for all the three methods. The RectangleArea method takes two parameters, length and breadth, and calculates the area of the rectangle by multiplying these two parameters. The SquareArea method takes one parameter, side, and calculates the area of the square by multiplying the side with itself. The CircleArea method takes one parameter, radius, and calculates the area of the circle using the formula pi times radius squared.

 

Finally, the main program creates an object of the Area class and calls all the three methods to calculate the area of a rectangle, square, and circle. The program outputs the results of the calculations using the System.out.println() statement.

The use of abstract classes and methods ensures that the subclasses implement these methods to provide their functionality. The implementation of the Area class uses inheritance to provide the implementation details for the Shape class's abstract methods.