public FastStringTokenizer(String str,
    boolean isLetter,
    boolean toLowerCase,
    Set stopWords) 
{
    
      this.str = str;
      this.isLetter = isLetter;
      this.toLowerCase = toLowerCase;
      this.stopWords = stopWords;
}

 public Token next() 
{
      // cache loop instance vars (performance)
      String s = str;
      int len = s.length();
      int i = pos;
      boolean letter = isLetter;
      int start = 0;
      String text;
      do {
        // find beginning of token
        text = null;
        while (i <  len && !isTokenChar(s.charAt(i), letter)) {
          i++;
        }
        if (i <  len) { // found beginning; now find end of token
          start = i;
          while (i <  len && isTokenChar(s.charAt(i), letter)) {
            i++;
          }
          text = s.substring(start, i);
          if (toLowerCase) text = text.toLowerCase(locale);
//          if (toLowerCase) {            
////            use next line once JDK 1.5 String.toLowerCase() performance regression is fixed
////            see http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6265809
//            text = s.substring(start, i).toLowerCase(); 
////            char[] chars = new char[i-start];
////            for (int j=start; j <  i; j++) chars[j-start] = Character.toLowerCase(s.charAt(j));
////            text = new String(chars);
//          } else {
//            text = s.substring(start, i);
//          }
        }
      } while (text != null && isStopWord(text));
      pos = i;
      return text != null ? new Token(text, start, i) : null;
}