Add each digit number until the sum value is less than 10

AddDigits.java

/**
 * Created by Daehee Han(@daniel_booknara) on 4/21/16.
 */
public class AddDigits {
    public static void main(String[] args) {
        int value = 38;
        System.out.println(addDigits(value));
    }

    public static int addDigits(int num) {
        while (num >= 10) {
            int sum = 0;

            while(num != 0) {
                int digit = num % 10;
                num = num / 10;

                sum += digit;
            }

            num = sum;
        }

        return num;
    }
}