Polymorphic code

Circle

public class Circle extends Shape 
{
  public Circle(double length) {
		super(length);	
	}
	
  @Override
  public double getArea() 
  {
    return length * length * Math.PI;
  }
  
  @Override
  public double getBoundaryLength() {
    return 2 * length * Math.PI;
  }
}

MyShapes

import java.util.Scanner;
 
public class MyShapes 
{
    public static Scanner scan = new Scanner(System.in);
 
    public static int Menu()
    {
        System.out.println("\nSelect a Shape or Exit: \n");
        System.out.println("1. Square");
        System.out.println("2. Circle");
        System.out.println("3. Triangle");
        System.out.println("4. Exit");
 
        System.out.println("\nEnter choice:");
        int option = scan.nextInt();
 
        return option;
    }// end menu
 
    public static void main(String[] args) 
    {       
        int option = 0;
 
        while (option != 4)
        {
            option = Menu();
 
            switch(option)
            {
                case 1:
                    Shape shape = new Circle(scan.nextDouble());
                    double boundaryLength = shape.getBoundaryLength();
                    double area = shape.getArea();
                    System.out.println("Boundary Length = " + Math.round(boundaryLength));
                    System.out.println("Area = " + Math.round(area));
                    break;
                    
                case 2:
                	Shape shape1 = new Square(scan.nextDouble());
                    double boundaryLength1 = shape1.getBoundaryLength();
                    double area1 = shape1.getArea();
                    System.out.println("Boundary Length = " + Math.round(boundaryLength1));
                    System.out.println("Area = " + Math.round(area1));
                    break;
                case 3:
                	Shape shape2 = new Triangle(scan.nextDouble());
                    double boundaryLength2 = shape2.getBoundaryLength();
                    double area2 = shape2.getArea();
                    System.out.println("Boundary Length = " + Math.round(boundaryLength2));
                    System.out.println("Area = " + Math.round(area2));
                    break;
                    
                case 4:
                    System.out.println("System closing");
                    System.out.println("-----------\n");
                    System.exit(0);
                    break;
                default:
                    System.out.println("Invalid option");
                    System.out.println("--------------\n");
            }
        }
    }
}

Shape

public abstract class Shape 
{
    protected double length;
    public Shape(double length) 
    {
      this.length = length;
    }
    public abstract double getArea();
    public abstract double getBoundaryLength();
}

Square

public class Square extends Shape 
{
  public Square(double length) {
		super(length);
		}
  
  @Override
  public double getArea() 
  {
    return length * length;
  }
  
  @Override
  public double getBoundaryLength()
  {
    return length * 4;
  }
}  

Triangle

public class Triangle extends Shape 
{
  public Triangle(double length) {
		super(length);
		 }
  
	  @Override
	  public double getArea() 
	  {
	    return 0.5 * length * length;
	  }
	  
	  @Override
	  public double getBoundaryLength() 
	  {
		  return (length + length) + Math.sqrt(2 * length * length);
	  }
}