Basic OOP concepts using Shapes

Circle.java

package com.bitrev.shapesbase;

public class Circle extends Shapes { // Circle is a shape therefore inherits properties of a shape
    private double radius;

    public Circle(double radius)
    {
        super(); // calling the parent class constructor
        this.radius = radius;
    }

    public double getRadius()
    {
        return this.radius;
    }

    public void setRadius(double radius)
    {
        this.radius = radius;
    }

    public void calculateArea()
    {
        double result = Math.PI * Math.pow(getRadius(), 2);
        setArea(result);
    }

    public void calculatePerimeter()
    {
        double result = 2 * Math.PI * getRadius();
        setPerimeter(result);
    }
}

Main.java

package com.bitrev.myapp;

import com.bitrev.shapesbase.Circle;
import com.bitrev.shapesbase.Shape;

public class Main {
    public static void main(String[] args) {
//        Calculate Area and Perimeter of Circle
        Circle c = new Circle(5.0); // Create new Circle object and set radius from constructor

        c.calculateArea();
        c.calculatePerimeter();

        // Realize that this method is not declared in Circle class?? That is because Circle inherits all
        // properties and methods(public) from the parent class Shapes
        c.displayArea();
        c.displayPerimeter();


        System.out.println();

        c.setRadius(10); // set radius of Circle from method

        c.calculateArea();
        c.calculatePerimeter();

        c.displayArea();
        c.displayPerimeter();
      
      // Do your own implementations of Rectangle, Triangle e.t.c here.
      // You first need to create classes for those shapes and inherit the Shapes class
    }
}

Shapes.java

package com.bitrev.shapesbase;

public class Shapes { // Shapes is a parent class that encompasses all shapes...circles, rectangles, triangles e.t.c
    private double area = 0.0; // from all shapes we can obtain an area
    private double perimeter = 0.0; // from all shapes we can obtain a perimeter

    public Shapes() {
    }

    public double getArea()
    {
        return area;
    }

    public void setArea(double area)
    {
        this.area = area;
    }

    public double getPerimeter()
    {
        return perimeter;
    }

    public void setPerimeter(double perimeter)
    {
        this.perimeter = perimeter;
    }

    public void displayArea() { // we can call this method for any object that's being referenced to at that time
        System.out.printf("The area of the shape is: %.2f%n", getArea());
    }

    public void displayPerimeter() // this can be combined with displayArea() to print in one line
    {
        // %.2f means print to 2 decimal places. f- decimal e.g. %f, d - integer e.g. %d, s - string e.g. %s
        // %n - means move cursor to a new line
        System.out.printf("The perimeter of the shape is: %.2f%n", getPerimeter());
    }
}