String (String separator) { if (separator.length() % 6 != 0) { return null; } StringBuilder result = new StringBuilder(); int pos = 0; while (pos < separator.length()) { String encodedCharacter = separator.substring(pos, pos+6); if (!encodedCharacter.startsWith("\\u")) { return null; } char code = (char) Integer.parseInt(encodedCharacter.substring(2), 16); result.append(code); pos += 6; } return result.toString(); }