static boolean isValidIdentifierName(String s)
    {
        int L = s.length();
        if (L == 0)
            return false;
        if (!Character.isJavaIdentifierStart(s.charAt(0)))
            return false;
        for (int i = 1; i != L; ++i) {
            if (!Character.isJavaIdentifierPart(s.charAt(i)))
                return false;
        }
        return !TokenStream.isKeyword(s);
    }