Java Conversion issue - Int to string and again

I am trying to make an integer to string to make slicing operation but the program doesn't gives me any answer it always gives the empty arraylist and While I see the modulus function simply returns the left but i want the modulus to return there.

public class My_first {
        public static void main(String[] args) {
                int left =1, right=22;
                ArrayList<Integer> num = new ArrayList<>();
                while(left<=right){
                        String number = Integer.toString(left);
                        int count =0;
                        for(int i=0;i<number.length();i++){
                                if(left % (int) number.charAt(i) == 0){
                                        count++;
                                }
                        }
                        left++;
                        if (count >=number.length()){
                                num.add(left);
                        }
                }
                System.out.println(num);
        }
}

Can anyone help me find out what is this issue here.. The output is to be {1,2,3,4,5,6,7,8,9,11,12,15,22}.

Thank you in advance!!!!!

Your code has a logical error in the modulus operation. The issue is with the expression (int) number.charAt(i). This line doesn't convert the character to its integer value, but rather to its ASCII value, which is not what you intend.

Try using Character.getNumericValue instead:

import java.util.ArrayList;

public class MyFirst {

    /**
     * Finds all numbers between left and right (inclusive) where each digit of the number
     * divides the number itself.
     *
     * @param left The starting number of the range.
     * @param right The ending number of the range.
     * @return An ArrayList containing numbers that meet the criteria.
     */
    public static ArrayList<Integer> findDivisibleNumbers(int left, int right) {
        ArrayList<Integer> numbers = new ArrayList<>();
        while (left <= right) {
            String number = Integer.toString(left);
            int count = 0;
            for (int i = 0; i < number.length(); i++) {
                int digit = Character.getNumericValue(number.charAt(i));
                if (digit != 0 && left % digit == 0) {
                    count++;
                }
            }
            if (count == number.length()) {
                numbers.add(left);
            }
            left++;
        }
        return numbers;
    }

    public static void main(String[] args) {
        ArrayList<Integer> numbers = findDivisibleNumbers(1, 22);
        System.out.println(numbers);
    }
}

Output:

[1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 15, 22]

Other changes:

• Added a check for digit != 0 to handle the case where left contains '0', as modulo by zero is undefined.
• Removed the underscore from your class name since that's unusual.
• Moved the algorithm into a separate method with corresponding Javadoc comment for increased readability and easy unit testing.

An alternate approach using streams for the culture:

import java.util.ArrayList;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

public static ArrayList<Integer> findDivisibleNumbers(int left, int right) {
    return IntStream.rangeClosed(left, right)
                    .filter(num -> {
                        String numberStr = Integer.toString(num);
                        return numberStr.chars()
                                        .map(Character::getNumericValue)
                                        .allMatch(digit -> digit != 0 && num % digit == 0);
                    })
                    .boxed()
                    .collect(Collectors.toCollection(ArrayList::new));
}