code: private static String checkForEmptyString(String s) {
          if (s == null) return null;
          if (s.length() == 0) return null;
  
          return s;
      }
docs: Checks if the specified string is empty or null and if so, returns null.
  Otherwise simply returns the string.
  
  @param s
  The string to check.
  @return Null if the specified string was null, or empty, otherwise
  returns the string the caller passed in.