public static String filter(String message) {
        if (message == null) return null;

        char[] content = new char[message.length()];
        message.getChars(0, message.length(), content, 0);
        StringBuilder result = new StringBuilder(content.length + 50);
        for (int i = 0; i < content.length; i++) {
            SpecialChar specialChar = SpecialChar.check(content[i]);
            if(specialChar != null) result.append(specialChar.toString());
            else result.append(content[i]);
        }
        return result.toString();
    }