Project 2 created by Ayysir - https://repl.it/@Ayysir/Project-2

Circle.java

//Circle class inherited from the shape

//class with implementation to the methods.

public class Circle extends Shape {

private int radius;

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

@Override
public void calculateArea() {

double area = Math.PI * (this.radius * this.radius);
System.out.println("Circle Area is : " + area);

}

@Override
public void display() {
System.out.println("Created Circle - radius : " + radius);
}

}

Rectangle.java

//Rectangle class inherited from shape with

//implementation to the methods.
public class Rectangle extends Shape {
private int length;
private int breadth;

public Rectangle(int length, int breadth) {
this.length = length;
this.breadth = breadth;
}
  
@Override
public void calculateArea() {
int area = this.length * this.breadth;
System.out.println("Rectange Area is : "+ area);
  
}

@Override
public void display() {
System.out.println(" Created Rectangle - Length : "+ length + " Breadth : "+ breadth);
}

}

Shape.java

//abstract class with unimplemented abstract methods.

interface Shape
{
public double calculateArea();
}

ShapeDriver.java

ShapeDriver.java

public class ShapeDriver {

public static void main(String args[]){
//creating a rectangle with length 10 and bredth 20
Shape rectangle = new Rectangle(10,20);
rectangle.display();
rectangle.calculateArea();
//creating a circle with radius 5.
Shape circle = new Circle(5);
circle.display();
circle.calculateArea();

Shape triangle = new Triangle(3,5,7);
triangle.calculateArea();
}
}

Triangle.java

public class Triangle extends Shape {
    private final double a, b, c; // sides

    public Triangle() {
        this(1,1,1);
    }
    public Triangle(double a, double b, double c) {
        this.a = a;
        this.b = b;
        this.c = c;
    }

    @Override
    public double calculateArea() {
        // Heron's formula:
        // A = SquareRoot(s * (s - a) * (s - b) * (s - c)) 
        // where s = (a + b + c) / 2, or 1/2 of the perimeter of the triangle 
        double s = (a + b + c) / 2;
        return Math.sqrt(s * (s - a) * (s - b) * (s - c));
    }
  
  @Override
public void display() {
System.out.println(" Created Triangle - Length : "+ length + " Breadth : "+ breadth);
}
}