code: public void whitespaceChars(int low, int hi) {
          if (low < 0) {
              low = 0;
          }
          if (hi > tokenTypes.length) {
              hi = tokenTypes.length - 1;
          }
          for (int i = low; i <= hi; i++) {
              tokenTypes[i] = TOKEN_WHITE;
          }
      }
docs: Specifies that the characters in the range from {@code low} to {@code hi}
  shall be treated as whitespace characters by this tokenizer.
  
  @param low
  the first character in the range of whitespace characters.
  @param hi
  the last character in the range of whitespace characters.