private void updateDocComboBoxInScheduleAppointment(Hospital hospital, JComboBox<String> comboBox) {
        comboBox.removeAllItems();
        HashMap<String, Person> allStaff = hospital.getAllStaff();
        for(Person person : allStaff.values()) {
            if(person.getType() == 2) {
                Doctor doc = (Doctor) person;
                comboBox.addItem(doc.getUserName());
            }
        }
    }