public boolean isFullFilled() {
		boolean isFilled = true;
		
		boolean aId = idActivity >= 0;
		boolean sTime = startTime != null;
		boolean eTime = endTime != null;
		boolean dur = duration >= 0;
		
		if (!aId) isFilled = false;
		if (!sTime) isFilled = false;
		if (!eTime) isFilled = false;
		if (!dur) isFilled = false;
		
		return isFilled;
	}