code: public LocalDateTime adjustTime(LocalDateTime time, boolean roundUp,
                                      DayOfWeek firstDayOfWeek) {
          requireNonNull(time);
  
          if (roundUp) {
              time = time.plus(getAmount(), getUnit());
          }
  
          return Util.truncate(time, getUnit(), getAmount(), firstDayOfWeek);
      }
docs: Adjusts the given time either rounding it up or down.
  
  @param time
  the time to adjust
  @param roundUp
  the rounding direction
  @param firstDayOfWeek
  the first day of the week (needed for rounding weeks)
  @return the adjusted time