code: public static String patternForTimestamp(
          DisplayMode dateMode,
          DisplayMode timeMode,
          Locale locale
      ) {
  
          String pattern = FORMAT_PATTERN_PROVIDER.getDateTimePattern(dateMode, timeMode, locale);
          return FormatUtils.removeZones(pattern);
  
      }
docs: /*[deutsch]
  <p>Liefert ein Formatmuster ohne Zeitzonensymbole f&uuml;r reine Zeitstempel. </p>
  
  @param   dateMode    display mode of date part
  @param   timeMode    display mode of time part
  @param   locale      language and country setting
  @return  format pattern for plain timestamps without timezone symbols
  @see     net.time4j.PlainTimestamp
  @since   3.13/4.10