PRACTICE QUESTIONS ON ABSTRACT CLASS – CLASS SHAPE

Create an abstract class “Shape” with abstract methods “getArea()” and “getPerimeter()”. Implement two subclasses “Rectangle” and “Circle” which extend “Shape” and implement the abstract methods. Create a “Square” class which extends “Rectangle” and overrides the necessary methods. Create objects of all classes and test their behavior.

Solution:

abstract class Shape {
    public abstract double getArea();
    public abstract double getPerimeter();
}

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

    public Rectangle(double length, double width) {
        this.length = length;
        this.width = width;
    }

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

    public double getPerimeter() {
        return 2 * (length + width);
    }
}

class Circle extends Shape {
    private double radius;

    public Circle(double radius) {
        this.radius = radius;
    }

    public double getArea() {
        return Math.PI * radius * radius;
    }

    public double getPerimeter() {
        return 2 * Math.PI * radius;
    }
}

class Square extends Rectangle {
    public Square(double side) {
        super(side, side);
    }

    public double getArea() {
        return super.getArea();
    }

    public double getPerimeter() {
        return super.getPerimeter();
    }
}

And here’s an example of how you can use these classes into main class:

public class AbstractExample {
    public static void main(String[] args) {
        Shape rectangle = new Rectangle(4, 6);
        Shape circle = new Circle(3);
        Shape square = new Square(5);

        System.out.println("Rectangle area: " + rectangle.getArea());
        System.out.println("Rectangle perimeter: " + rectangle.getPerimeter());

        System.out.println("Circle area: " + circle.getArea());
        System.out.println("Circle perimeter: " + circle.getPerimeter());

        System.out.println("Square area: " + square.getArea());
        System.out.println("Square perimeter: " + square.getPerimeter());
    }
}

Save the above Program with “AbstractExample .Java” then compile it with the following command :

javac AbstractExample.java //to compile the code

java AbstractExample //to run the code

Output is :

Rectangle area: 24.0
Rectangle perimeter: 20.0
Circle area: 28.274333882308138
Circle perimeter: 18.84955592153876
Square area: 25.0
Square perimeter: 20.0

Want to practice more problems involving Abstract Classes? Click here.