Error says it's dividing by zero while it's not initialised as zero

Question

Im trying to find if the number is automorphic, the code compiles fine but it says there is divide by zero on the line where i've marked it

import java.util.Scanner;
class AutoLoop
{
    public static void main()
    {
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter a number to check if it's automorphic or not");
        int num = sc.nextInt();
        int sqr = num*num;
        int sqrSave=sqr;
        int divisor = 10;
        int counter = 1;
        while (counter<=100)
        {
            sqr = sqr%divisor;  //It says there is divide by zero error on this line
            if (sqr==num)
            {
                System.out.println("Number is an automorphic number");
                break;
            }
            sqr=sqrSave;
            divisor*=10;
            counter++;
            if (counter == 100)
                 System.out.println("Number is not an automorphic number till the 100th digit.");
        }
    }
}

i've already tried making it sqr%=divisor; still doesn't work.

Answer 1

I've tested your code and it seems to be that you try to multiply the divisor variable past the 32 bit integer limit, and since that is not possible, it becomes some other numbers, and after a while it turns into a zero. This happens every time you enter an non-automorphic number

This is the value of the divisor every time your code loops around:

10

100

1000

10000

100000

1000000

10000000

100000000

1000000000

1410065408

1215752192

-727379968

1316134912

276447232

-1530494976

1874919424

1569325056

-1486618624

-1981284352

1661992960

-559939584

-1304428544

-159383552

-1593835520

1241513984

-469762048

-402653184

268435456

-1610612736

1073741824

-2147483648

0

A fix for this may be to make the divisor an double or float instead of an integer