code: public static boolean isValidClassName(String s) {
          if (s.length() < 1) return false;
          if (s.equals("package-info")) return true;
          if (surrogatesSupported) {
              int cp = s.codePointAt(0);
              if (!Character.isJavaIdentifierStart(cp))
                  return false;
              for (int j = Character.charCount(cp); j < s.length(); j += Character.charCount(cp)) {
                  cp = s.codePointAt(j);
                  if (!Character.isJavaIdentifierPart(cp))
                      return false;
              }
          } else {
              if (!Character.isJavaIdentifierStart(s.charAt(0)))
                  return false;
              for (int j = 1; j < s.length(); j++)
                  if (!Character.isJavaIdentifierPart(s.charAt(j)))
                      return false;
          }
          return true;
      }
docs: Return true if given file name is a valid class name
  (including "package-info").
  @param s the name of the class to check.
  @return true if given class name is a valid class name
  and false otherwise.