Java: Abstract GeometricShape Class with Triangle and Square Subclasses

Java Abstract Class: Exercise-12 with Solution

Write a Java program to create an abstract class GeometricShape with abstract methods area() and perimeter(). Create subclasses Triangle and Square that extend the GeometricShape class and implement the respective methods to calculate the area and perimeter of each shape.

Sample Solution:

Java Code:

// GeometricShape.java
// Define an abstract class named GeometricShape
abstract class GeometricShape {
  // Declare an abstract method named area that returns a double
  public abstract double area();

  // Declare an abstract method named perimeter that returns a double
  public abstract double perimeter();
} 

// Triangle.java
// Define a class named Triangle that extends GeometricShape
class Triangle extends GeometricShape {
  // Declare private instance variables for the sides of the triangle
  private double side1;
  private double side2;
  private double side3;

  // Define a constructor that initializes the sides of the triangle
  public Triangle(double side1, double side2, double side3) {
    // Assign the parameters to the instance variables
    this.side1 = side1;
    this.side2 = side2;
    this.side3 = side3;
  }

  // Override the area method from GeometricShape
  @Override
  // Implementation of the area method that calculates and returns the area of the triangle
  public double area() {
    // Calculate the semi-perimeter of the triangle
    double s = (side1 + side2 + side3) / 2;
    // Calculate and return the area using Heron's formula
    return Math.sqrt(s * (s - side1) * (s - side2) * (s - side3));
  }

  // Override the perimeter method from GeometricShape
  @Override
  // Implementation of the perimeter method that returns the perimeter of the triangle
  public double perimeter() {
    // Return the sum of the sides of the triangle
    return side1 + side2 + side3;
  }
} 

// Square.java
// Define a class named Square that extends GeometricShape
class Square extends GeometricShape {
  // Declare a private instance variable for the side of the square
  private double side;

  // Define a constructor that initializes the side of the square
  public Square(double side) {
    // Assign the parameter to the instance variable
    this.side = side;
  }

  // Override the area method from GeometricShape
  @Override
  // Implementation of the area method that calculates and returns the area of the square
  public double area() {
    // Calculate and return the area by squaring the side length
    return side * side;
  }

  // Override the perimeter method from GeometricShape
  @Override
  // Implementation of the perimeter method that returns the perimeter of the square
  public double perimeter() {
    // Calculate and return the perimeter by multiplying the side length by 4
    return 4 * side;
  }
} 

// Define the Main class
public class Main {
  // Main method: entry point of the program
  public static void main(String[] args) {
    // Create a Triangle object with sides 4, 5, and 6
    GeometricShape triangle = new Triangle(4, 5, 6);
    // Create a Square object with side length 6
    GeometricShape square = new Square(6);

    // Print the area of the triangle
    System.out.println("Triangle Area: " + triangle.area());
    // Print the perimeter of the triangle
    System.out.println("Triangle Perimeter: " + triangle.perimeter());

    // Print the area of the square
    System.out.println("Square Area: " + square.area());
    // Print the perimeter of the square
    System.out.println("Square Perimeter: " + square.perimeter());
  }
}

Output:

Triangle Area: 9.921567416492215
Triangle Perimeter: 15.0
Square Area: 36.0
Square Perimeter: 24.0

Explanation:

In the above exercise -

• The abstract class GeometricShape has two abstract methods: area() and perimeter(). The subclasses Triangle and Square extend the GeometricShape class and provide their own implementations for these abstract methods.
• The "Triangle" class calculates the area and perimeter of a triangle using its three sides, while the "Square" class calculates the area and perimeter of a square using its side length.
• In the main method, we create instances of Triangle and Square, and then call the area() and perimeter() methods on each object to calculate and display the respective area and perimeter.

Flowchart:

Java Code Editor:

Contribute your code and comments through Disqus.

Previous: Abstract Bird Class with Eagle and Hawk Subclasses.