code: public static DayOfWeek plus(final DayOfWeek self, int days) {
          int daysPerWeek = DayOfWeek.values().length;
          int val = ((self.getValue() + days - 1) % daysPerWeek) + 1;
          return DayOfWeek.of(val > 0 ? val : daysPerWeek + val);
      }
docs: Returns the {@link java.time.DayOfWeek} that is {@code days} many days after this day of the week.
  
  @param self a DayOfWeek
  @param days the number of days to move forward
  @return the DayOfWeek
  @since 2.5.0