Why is this insertion sort code of java throwing exception

Question

The question was to sort the digits of a number in ascending order using insertion sort. this code of mine throws exception at the arr[i] = num %10; line..

import java.util.Scanner;

public class Insertion_sort {

    
    Scanner sc = new Scanner(System.in);
    int num = sc.nextInt();
    int count;
    int temp = num;

    public void counting() {
         while (temp > 0) {
             temp= temp / 10;
              count++;
         }

    }
    int []arr = new int[count];
     public void solutions() {
         for (int i = 0; i < count; i++) {
              arr[i] = num % 10;
              num = num / 10;
         }
         for (int i = 1; i < count; i++) {
              int var = arr[i];
              int j = i;
              while (j > 0 && arr[j - 1] > var) {
                   arr[j] = arr[j - 1];
                   j--;
              }
              arr[j] = var;
         }
         for (int i= 0; i< count; i++) {
              System.out.println(arr[i]);
         }
    }


    public static void main(String[] args) {
         Insertion_sort obj = new Insertion_sort();
         obj.solutions();
         
    }
}