Why 3rd test doesnt work in Java course in 56. lesson Shape project?

Question

import java.util.Scanner;

abstract class Shape {
int width;
abstract void area();
}
//your code goes here
class Square extends Shape{
Square(int x) {
this.width = x;
}
public void area() {
System.out.println(this.width*this.width);
}
}
class Circle extends Shape {
Circle(int y) {
this.width = y;
}
public void area() {
System.out.println(this.width*this.width*Math.PI);
}
}

public class Program {
public static void main(String[ ] args) {
Scanner sc = new Scanner(System.in);
int x = sc.nextInt();
int y = sc.nextInt();

Square a = new Square(x);
Circle b = new Circle(y);
a.area();
b.area();
}
}

Answer 1

Try

System.out.println(Math.PI*this.width*this.width) ;

Answer 2

It helps, thank you.

Answer 3

It works for me too, but I don't understand why!