Java Inheritance Programming - Create a class called Shape with methods called getPerimeter() and getArea()

Java Inheritance: Exercise-8 with Solution

Write a Java program to create a class called Shape with methods called getPerimeter() and getArea(). Create a subclass called Circle that overrides the getPerimeter() and getArea() methods to calculate the area and perimeter of a circle.

Sample Solution:

Java Code:

// Shape.java
// Parent class Shape

// Declare the Shape class
public class Shape {
    
    // Public method to get the perimeter of the shape, returning a default value of 0.0
    public double getPerimeter() {
        return 0.0;
    }

    // Public method to get the area of the shape, returning a default value of 0.0
    public double getArea() {
        return 0.0;
    }
}

// Circle.java
// Child class Circle

// Declare the Circle class which extends the Shape class
public class Circle extends Shape {
    
    // Private instance variable for the radius of the circle
    private double radius;

    // Constructor for the Circle class, taking the radius as a parameter
    public Circle(double radius) {
        // Initialize the radius instance variable
        this.radius = radius;
    }

    // Override the getPerimeter method from the superclass (Shape)
    @Override
    public double getPerimeter() {
        // Return the perimeter of the circle calculated as 2 * π * radius
        return 2 * Math.PI * radius;
    }

    // Override the getArea method from the superclass (Shape)
    @Override
    public double getArea() {
        // Return the area of the circle calculated as π * radius^2
        return Math.PI * radius * radius;
    }
}

// Main.java
// Main class

// Declare the Main class
public class Main {
    
    // Main method to execute the program
    public static void main(String[] args) {
        
        // Declare a double variable r and initialize it to 8.0
        double r = 8.0;
        
        // Create a Circle object named c1 with radius r
        Circle c1 = new Circle(r);
        
        // Print the radius of the circle c1
        System.out.println("Radius of the circle=" + r);
        
        // Print the perimeter of the circle c1
        System.out.println("Perimeter: " + c1.getPerimeter());
        
        // Print the area of the circle c1
        System.out.println("Area: " + c1.getArea());
        
        // Update the value of r to 3.2
        r = 3.2;
        
        // Create a Circle object named c2 with radius r
        Circle c2 = new Circle(r);
        
        // Print the radius of the circle c2
        System.out.println("\nRadius of the circle=" + r);
        
        // Print the perimeter of the circle c2
        System.out.println("Perimeter: " + c2.getPerimeter());
        
        // Print the area of the circle c2
        System.out.println("Area: " + c2.getArea());
    }
} 

Output:

Radius of the circle=8.0
Perimeter: 50.26548245743669
Area: 201.06192982974676

Radius of the circle=3.2
Perimeter: 20.106192982974676
Area: 32.169908772759484 

Explanation:

In the above exercise, the Shape class is a base class that provides generic methods for calculating the perimeter and area of a shape. The Circle class is a subclass that extends Shape and overrides the getPerimeter() and getArea() methods to implement circle formulas.

The Circle class has a private radius field that takes a radius argument to initialize the field. The getPerimeter() method uses the formula 2πr to calculate the circumference of the circle. The getArea() method uses the formula πr^2 to calculate the circle area.

In the Main class -

The given code creates two Circle objects, c1 and c2, and calculates their perimeter and area using the getPerimeter() and getArea() methods. The radius of each circle is first set using a double variable r. The output displays the radius, perimeter, and area of each circle.

Flowchart:

Java Code Editor:

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