code: public final void setStartDate(Date startDate) {
                  if (this.startDate == null || !this.startDate.equals(startDate)) {
                          if (startDate != null && endDate != null && endDate.before(startDate)) {
                                  throw new ParameterException("The start date must be before the end date of the filter.");
                          }
                          this.startDate = startDate;
                          setChanged();
                          notifyObservers();
                  }
          }
docs: Sets the start date.
  
  @param startDate