code: public static String formatDate(Date date, String pattern) {
          if (date == null) throw new IllegalArgumentException("date is null");
          if (pattern == null) throw new IllegalArgumentException("pattern is null");
  
          SimpleDateFormat formatter = DateFormatHolder.formatFor(pattern);
          return formatter.format(date);
      }
docs: Formats the given date according to the specified pattern.  The pattern
  must conform to that used by the {@link SimpleDateFormat simple date
  format} class.
  
  @param date The date to format.
  @param pattern The pattern to use for formatting the date.
  @return A formatted date string.
  
  @throws IllegalArgumentException If the given date pattern is invalid.
  
  @see SimpleDateFormat