why one from five tests of this code outputs error? (More on classes - 56 Code project)

Question

import java.util.Scanner;

abstract class Shape {
int width;
abstract void area();
Shape (int w) {
this.width = w;
}
}

public class Square extends Shape {
Square (int w) {
super(w);
}
void area () {
System.out.println(width*width);
}
}

public class Circle extends Shape {
Circle (int w) {
super(w);
}
void area () {
System.out.println((double)(width*width)*Math.PI);
}
}
//введите код сюда

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 this :

void area () {
System.out.println((double)width*width*Math.PI);
}

Or

void area () {
System.out.println(Math.PI*width*width);
}