Number-to-words translator

Question

I've created a class that translates an integer into words in an English (not British) format. My first human language is not English, and I don't have a good idea of a truly right way to read numbers, so I followed the exact meaning of the numbers (e.g. 1024 = one thousand twenty-four, not ten twenty-four as read by some humans).

public class NumsToWords {  
    private static String[] ones = {"","one","two","three","four","five","six","seven","eight","nine","ten","eleven","twelve","thirteen","fourteen","fifteen","sixteen","seventeen","eighteen","nineteen"};
    private static String[] tens = {"","","twenty","thirty","forty","fifty","sixty","seventy","eighty","ninety"};
    private static String hundred = " hundred ";
    private static String[] all = {"","thousand","million","billion","trillion","quadrillion"}; 

    public static String translate(String number) {
        StringBuilder res = new StringBuilder();
        StringBuilder mutableNumber = new StringBuilder(number);
        int numberLength = number.length();

        // totalTypes is my way of separating the digits in to groups that has three digits each, a ones, tens and hundreds. For example 123456 has two. A thousands part (123) and normal digits (456)
        int totalTypes = numberLength/3;
        // leadingDigits is my way of finding out of not all parts of a number is complete. That is. in 12345, 12 is the thousand part, not 123.
        int leadingDigits = numberLength%3;
        if (leadingDigits > 0) {
            insertWords(res, mutableNumber, leadingDigits, totalTypes);
        }
        totalTypes--;
        for (int i = leadingDigits; i < numberLength; i+= 3) {
            insertWords(res, mutableNumber, 3, totalTypes--);
        }
        return res.toString().trim();
    }

    // translate numbers that are present in all types (ones, tens and hundreds)
    private static StringBuilder translateHundreds(String number) {
        StringBuilder res = new StringBuilder();
        if (number.equals("0")) {
            res.append("zero");
        } else {
            int intNumber = Integer.parseInt(number);
            if (intNumber >= ones.length) {
                StringBuilder digits = new StringBuilder(number);
                if (digits.length() == 2) {
                    res.append(tens[next(digits)]);
                    String one = ones[next(digits)];
                    if (!one.isEmpty()) {
                        res.append("-"+one);
                    }
                }
                if (digits.length() == 3) {
                    int hundredVal = next(digits);
                    res.append(hundredVal == 0 ? "" : ones[hundredVal]+hundred).append(translateHundreds(number.substring(1))); 
                }
            } else {
                res.append(ones[intNumber]);
            }
        }
        return res;
    }

    private static void insertWords(StringBuilder res, StringBuilder number, int end, int index) {
        StringBuilder trans = translateHundreds(number.substring(0, end));
        if (trans.length() > 0) {
            res.append(trans).append(" "+all[index]+" ");
        }
        number.delete(0, end);
    }

    // read values from part of a number not exceeding three digits
    private static int next(StringBuilder str) {
        int res = Integer.parseInt(str.substring(0,1));
        str.delete(0, 1);
        return res;
    }
}

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