private boolean compareArzt(Arzt first, Arzt second) {
boolean strings =
(first.getPrename().equals(second.getPrename())
&& first.getSurname().equals(second.getSurname())
&& first.getBehandelndeKrankheit().equals(second.getBehandelndeKrankheit()));
boolean op = true;
if (first.getOpTermin() == null && second.getOpTermin() == null) {
op = true;
} else if (first.getOpTermin() == null ^ second.getOpTermin() == null) {
op = false;
} else if (first.getOpTermin().compareTo(second.getOpTermin()) != 0) {
op = false;
}
return strings && op;
}
