code: public static String parse(String timeZone) {
  
          // Return null if no time zone provided
          if (timeZone == null || timeZone.isEmpty())
              return null;
  
          // Otherwise, assume time zone is valid
          return timeZone;
  
      }
docs: Parses the given string into a time zone ID string. As these strings are
  equivalent, the only transformation currently performed by this function
  is to ensure that a blank time zone string is parsed into null.
  
  @param timeZone
  The time zone string to parse, which may be null.
  
  @return
  The ID of the time zone corresponding to the given string, or null
  if the given time zone string was null or blank.