Number Speller

package com.cyecize.app;

import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Scanner;

public class StartUp {

    static final Map<Integer, String> numbersMapping = new HashMap<>() {{
        put(0, "Zero");
        put(1, "One");
        put(2, "Two");
        put(3, "Three");
        put(4, "Four");
        put(5, "Five");
        put(6, "Six");
        put(7, "Seven");
        put(8, "Eight");
        put(9, "Nine");
        put(10, "Ten");
        put(11, "Eleven");
        put(12, "Twelve");
        put(13, "Thirteen");
        put(14, "Fourteen");
        put(15, "Fifteen");
        put(16, "Sixteen");
        put(17, "Seventeen");
        put(18, "Eighteen");
        put(19, "Nineteen");
        put(20, "Twenty");
        put(30, "Thirty");
        put(40, "Forty");
        put(50, "Fifty");
        put(60, "Sixty");
        put(70, "Seventy");
        put(80, "Eighty");
        put(90, "Ninety");
    }};

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        while (true) {
            String line = scanner.nextLine();
            if ("end".equalsIgnoreCase(line)) break;

            int number = Integer.parseInt(line);
            System.out.println(spellNumber(number));
        }
    }

    static String spellNumber(Integer num) {
        if (num < 0) {
            return "Minus " + spellNumber(Math.abs(num));
        }
        if (numbersMapping.containsKey(num)) {
            return numbersMapping.get(num);
        }

        int numLength = num.toString().length();
        if (NumberSuffix.hasSuffix(numLength)) {
            NumberSuffix suffix = NumberSuffix.getSuffix(numLength);

            int numberChunk = num / suffix.division;
            int leftover = num % suffix.division;

            String numberName = spellNumber(numberChunk) + " " + suffix.suffix;
            if (leftover == 0) {
                return numberName;
            }

            if (leftover < 100 && num >= 100) {
                numberName += " and";
            }

            return numberName + " " + spellNumber(leftover);
        }

        //Code is only reachable for numbers in range from 21 to 99
        if (num > 99) {
            return "Number too big!";
        }

        int decimalRounded = num / 10 * 10;
        int leftover = num % 10;

        String numberName = spellNumber(decimalRounded);
        if (leftover == 0) {
            return numberName;
        }

        return numberName + " " + spellNumber(leftover);
    }

    static enum NumberSuffix {
        HUNDRED(List.of(3), "Hundred", 100),
        THOUSAND(List.of(4, 5, 6), "Thousand", 1000),
        MILLION(List.of(7), "Million", 1000000);

        final List<Integer> numLengths;
        final String suffix;
        final int division;

        NumberSuffix(List<Integer> numLengths, String suffix, int division) {
            this.numLengths = numLengths;
            this.suffix = suffix;
            this.division = division;
        }

        static NumberSuffix getSuffix(int numLength) {
            return Arrays.stream(values()).filter(val -> val.numLengths.contains(numLength)).findFirst().orElse(null);
        }

        static boolean hasSuffix(int numLenght) {
            return getSuffix(numLenght) != null;
        }
    }
}