}
      checkState(!hasLowerCase(), "Cannot call lowerCase() on a mixed-case alphabet");
      char[] lowerCased = new char[chars.length];
      for (int i = 0; i < chars.length; i++) {
        lowerCased[i] = Ascii.toLowerCase(chars[i]);
      }
      Alphabet lowerCase = new Alphabet(name + ".lowerCase()", lowerCased);
      return ignoreCase ? lowerCase.ignoreCase() : lowerCase;
    }

    public boolean matches(char c) {