public void create(Stewardess stewardess) {
   if (stewardess == null) {
     throw new NullPointerException("Destination is null when it is created");
   }
   if (stewardess.getId() == null) {
     stewardess.setId(Long.valueOf(idSequence));
     idSequence++;
   }
   mockDB.add(stewardess);
 }
 public Stewardess get(Long id) {
   if (id == null) {
     throw new NullPointerException("Id destination is null ");
   }
   for (Stewardess dest : mockDB) {
     if (dest.getId().equals(id)) {
       return dest;
     }
   }
   return null;
 }
 public void remove(Stewardess stewardess) {
   if (stewardess == null) {
     throw new NullPointerException("Stewardess is null when it is removed");
   }
   int index = -1;
   for (int i = 0; i < mockDB.size(); i++) {
     if (stewardess.getId().equals(mockDB.get(i).getId())) {
       index = i;
       break;
     }
   }
   if (index != -1) {
     mockDB.remove(index);
   }
 }
 public void update(Stewardess stewardess) {
   if (stewardess == null) {
     throw new NullPointerException("Destination is null when it is updated");
   }
   for (Stewardess stewardess1 : mockDB) {
     if (stewardess1.getId().equals(stewardess.getId())) {
       stewardess1.setBirthNumber(stewardess.getBirthNumber());
       stewardess1.setName(stewardess.getName());
       stewardess1.setSurname(stewardess.getSurname());
       stewardess1.setSex(stewardess.getSex());
     }
   }
 }