Array add - interview task

ArrayAdd.java

package com.company;

import java.util.Arrays;

public class ArrayAdd {
    public static int[] incArray(int[] digits, int base) {
        assert base > 0;
        final int[] result = new int[digits.length + 1];
        int carry = 1; // Increment value
        for (int i = digits.length - 1; i >= 0; i--) {
            assert digits[i] < base;
            if ((digits[i] + carry) >= (base - 1)) {
                result[i + 1] = 0;
                carry = 1;
            } else {
                result[i + 1] = digits[i] + carry;
                carry = 0;
            }
        }
        if (carry > 0)
            result[0] = carry;
        return result;
    }

    public static int[] incArrayV2(final int[] digits, final int increment, final int base) {
        assert base > 0;
        final int[] result = new int[digits.length + 1];
        int carry = increment;
        for (int i = digits.length - 1; i >= 0; i--) {
            assert digits[i] >= 0;
            final int d = digits[i] + carry;
            result[i + 1] = Math.floorMod(d, base);
            carry = d / base;
        }
        if (carry > 0)
            result[0] = carry;
        return result;
    }

    public static void main(String[] args) {
        System.out.println(Arrays.toString(incArrayV2(new int[]{1, 3, 9}, 12, 10)));
    }
}