Java Polymorphism - Shape Class with Circle, Rectangle, and Triangle Subclasses for Area and Perimeter Calculation

Java Polymorphism: Exercise-6 with Solution

Write a Java program to create a class Shape with methods getArea() and getPerimeter(). Create three subclasses: Circle, Rectangle, and Triangle. Override the getArea() and getPerimeter() methods in each subclass to calculate and return the area and perimeter of the respective shapes.

In the given exercise, here is a simple diagram illustrating polymorphism implementation:

Polymorphism: Shape Class with Circle, Rectangle, and Triangle Subclasses for Area and Perimeter Calculation

In the above diagram, the Circle, Rectangle, and Triangle classes have the getArea() and getPerimeter() methods. These methods allow them to calculate and return the area and perimeter specific to each shape.

Sample Solution:

Java Code:

// Shape.java
// Base class Shape
abstract class Shape {
    public abstract double getArea();
    public abstract double getPerimeter();

// Circle.java
// Subclass Circle
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;
// Rectangle.java
// Subclass Rectangle
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);
// Triangle.java
// Subclass Triangle

class Triangle extends Shape {
    private double side1;
    private double side2;
    private double side3;

    public Triangle(double side1, double side2, double side3) {
        this.side1 = side1;
        this.side2 = side2;
        this.side3 = side3;

    public double getArea() {
        double s = (side1 + side2 + side3) / 2;
        return Math.sqrt(s * (s - side1) * (s - side2) * (s - side3));

    public double getPerimeter() {
        return side1 + side2 + side3;
// Main.java
// Main class
public class Main {
    public static void main(String[] args) {
		double r = 4.0;
        Circle circle = new Circle(r);
		double rs1 = 4.0, rs2 = 6.0;
		double ts1 = 3.0, ts2 = 4.0, ts3 = 5.0;
        Rectangle rectangle = new Rectangle(rs1, rs2);
        Triangle triangle = new Triangle(ts1, ts2, ts3);
        System.out.println("Radius of the Circle"+r);
        System.out.println("Area of the Circle: " + circle.getArea());
        System.out.println("Perimeter of the Circle: " + circle.getPerimeter());
		System.out.println("\nSides of the rectangle are: "+rs1+','+rs2);
        System.out.println("Area of the Rectangle: " + rectangle.getArea());
        System.out.println("Perimeter of the Rectangle: " + rectangle.getPerimeter());
		System.out.println("\nSides of the Traiangel are: "+ts1+','+ts2+','+ts3);
        System.out.println("Area of the Triangle: " + triangle.getArea());
        System.out.println("Perimeter of the Triangle: " + triangle.getPerimeter());

Sample Output:

Radius of the Circle4.0
Area of the Circle: 50.26548245743669
Perimeter of the Circle: 25.132741228718345

Sides of the rectangle are: 4.0,6.0
Area of the Rectangle: 24.0
Perimeter of the Rectangle: 20.0

Sides of the Traiangel are: 3.0,4.0,5.0
Area of the Triangle: 6.0
Perimeter of the Triangle: 12.0


Flowchart: Base class Shape
Flowchart: Subclass Circle
Flowchart: Subclass Rectangle
Flowchart: Subclass Triangle
Flowchart: Main class

Java Code Editor:

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Java: Tips of the Day

How do I remove repeated elements from ArrayList?

If you don't want duplicates in a Collection, you should consider why you're using a Collection that allows duplicates. The easiest way to remove repeated elements is to add the contents to a Set (which will not allow duplicates) and then add the Set back to the ArrayList:

Set<String> set = new HashSet<>(yourList);

Of course, this destroys the ordering of the elements in the ArrayList.

Ref: https://bit.ly/3bYIjNC


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