if (spaceChars == null) {
            if (spaceStr.startsWith("u")) {
                spaceChars = split(spaceStr, "u")
                        .get(stream -> stream.filter(StringUtil::isNotBlank).mapToInt(s -> Integer.parseInt(s, 16)).toArray());
            } else {
                // backward compatibility
                final int length = spaceStr.length();
                spaceChars = new int[length];