How to get the separate digits of an int number?

Question

I have numbers like 1100, 1002, 1022 etc. I would like to have the individual digits, for example for the first number 1100 I want to have 1, 1, 0, 0.

How can I get

Answer 1

How about this?

public static void printDigits(int num) {
    if(num / 10 > 0) {
        printDigits(num / 10);
    }
    System.out.printf("%d ", num % 10);
}

or instead of printing to the console, we can collect it in an array of integers and then print the array:

public static void main(String[] args) {
    Integer[] digits = getDigits(12345);
    System.out.println(Arrays.toString(digits));
}

public static Integer[] getDigits(int num) {
    List digits = new ArrayList();
    collectDigits(num, digits);
    return digits.toArray(new Integer[]{});
}

private static void collectDigits(int num, List digits) {
    if(num / 10 > 0) {
        collectDigits(num / 10, digits);
    }
    digits.add(num % 10);
}

If you would like to maintain the order of the digits from least significant (index[0]) to most significant (index[n]), the following updated getDigits() is what you need:

/**
 * split an integer into its individual digits
 * NOTE: digits order is maintained - i.e. Least significant digit is at index[0]
 * @param num positive integer
 * @return array of digits
 */
public static Integer[] getDigits(int num) {
    if (num < 0) { return new Integer[0]; }
    List digits = new ArrayList();
    collectDigits(num, digits);
    Collections.reverse(digits);
    return digits.toArray(new Integer[]{});
}