Leetcode: Integer to English Words

Convert a non-negative integer to its english words representation. Given input is guaranteed to be less than 231 - 1.

For example,
123 -> "One Hundred Twenty Three"
12345 -> "Twelve Thousand Three Hundred Forty Five"
1234567 -> "One Million Two Hundred Thirty Four Thousand Five Hundred Sixty Seven"

Career Cup 150 Pg 442

Think of Convert(19,323,984) = Process(19) + "million" + Process(323) + "thousand" + Process(984) + ""

The Process is a process that generates words representation for integer below 1000

public class Solution {
    String[] digits = new String[]{"One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine"};
    String[] teen = new String[]{"Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen"};
    String[] tens = new String[]{"Ten", "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety"};
    String[] bigs = new String[]{"", "Thousand", "Million", "Billion"};
    
    public String numberToWords(int num) {
        String res = new String();
        if (num == 0) return "Zero";
        int count = 0;
        while (num > 0) {
            int belowThousand = num % 1000;
            if (belowThousand != 0) {
                res = process(belowThousand) + " " + bigs[count] + " " + res;
            }
            count++;
            num = num / 1000;
        }
        return res.trim();
    }
    
    public String process(int n) {
        String res = new String();
        if (n/100 > 0) {
            res = digits[n/100-1] + " " + "Hundred" + " ";
            n = n%100;
        }
        if (n>=11 && n<=19) {
            res = res + teen[n%10-1];
            return res;
        }
        else if (n/10 > 0) {
            res = res + tens[n/10-1] + " ";
            n = n%10;
        }
        if (n > 0) {
            res = res + digits[n-1];
        }
        return res.trim();
    }
}