code: private static boolean isAlpha(int c) {
          return (c >= '0' && c <= '9') ||
                 (c >= 'A' && c <= 'Z') ||
                 (c == ' ') ||
                 (c == '$') ||
                 (c == '%') ||
                 (c == '*') ||
                 (c == '+') ||
                 (c == '-') ||
                 (c == '.') ||
                 (c == '/') ||
                 (c == ':');
      }
docs: Returns true if input is in the Alphanumeric set (see Table J.1)