code: public static List<DayOfTheWeek> getAll() {
          final List<DayOfTheWeek> days = new ArrayList<>();
          for (final DayOfTheWeek day : ALL) {
              days.add(day);
          }
          return Collections.unmodifiableList(days);
      }
docs: Returns a list of the weekdays ordered by the id (Mon-Sun,PH).
  
  @return Unmodifiable list.