code: private SortedSet<WeekDay> readWeekDays(JSONValue val) {
  
          JSONArray array = null == val ? null : val.isArray();
          if (null != array) {
              SortedSet<WeekDay> result = new TreeSet<>();
              for (int i = 0; i < array.size(); i++) {
                  try {
                      result.add(readWeekDay(array.get(i)));
                  } catch (@SuppressWarnings("unused") IllegalArgumentException e) {
                      // Just skip
                  }
              }
              return result;
          }
          return new TreeSet<>();
      }
docs: Reads the weekday information.
  @param val the JSON object containing the weekday information.
  @return the weekdays extracted, defaults to the empty list, if no information is found.