code: public static String parse(String str) {
  
          // Return null if no value provided
          if (str == null || str.isEmpty())
              return null;
  
          // Otherwise, return string unmodified
          return str;
  
      }
docs: Parses the given string, interpreting empty strings as equivalent to
  null. For all other cases, the given string is returned verbatim.
  
  @param str
  The string to parse, which may be null.
  
  @return
  The given string, or null if the given string was null or empty.