@NotNull
    private static String replacement(RegExpChar aChar) {
      final int codePoint = aChar.getValue();
      return Character.isSupplementaryCodePoint(codePoint)
             ? Character.toString(Character.highSurrogate(codePoint)) + Character.lowSurrogate(codePoint)
             : Character.toString((char)codePoint);
    }
@NotNull
    private static String replacement(RegExpChar aChar)