How to convert a number to words (in Java)

// This snippet may be used freely, as long as the authorship note remains in the source code.

private static final String[] lowNames = {
   "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten",
   "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"};

private static final String[] tensNames = {
   "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"};

private static final String[] bigNames = {
   "thousand", "million", "billion"};

/**
* Converts an integer number into words (american english).
* @author Christian d'Heureuse, Inventec Informatik AG, Switzerland, www.source-code.biz
**/
public static String convertNumberToWords (int n) {
   if (n < 0) {
      return "minus " + convertNumberToWords(-n); }
   if (n <= 999) {
      return convert999(n); }
   String s = null;
   int t = 0;
   while (n > 0) {
      if (n % 1000 != 0) {
         String s2 = convert999(n % 1000);
         if (t > 0) {
            s2 = s2 + " " + bigNames[t-1]; }
         if (s == null) {
            s = s2; }
          else {
            s = s2 + ", " + s; }}
      n /= 1000;
      t++; }
   return s; }

// Range 0 to 999.
private static String convert999 (int n) {
   String s1 = lowNames[n / 100] + " hundred";
   String s2 = convert99(n % 100);
   if (n <= 99) {
      return s2; }
    else if (n % 100 == 0) {
      return s1; }
    else {
      return s1 + " " + s2; }}

// Range 0 to 99.
private static String convert99 (int n) {
   if (n < 20) {
      return lowNames[n]; }
   String s = tensNames[n / 10 - 2];
   if (n % 10 == 0) {
      return s; }
   return s + "-" + lowNames[n % 10]; }

Author: Christian d'Heureuse (www.source-code.biz, www.inventec.ch/chdh)
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