List.removeAll(otherList) - wrong result

Question

Hi guys,
I have 2 Lists:
1.     carList
2.     documentList
*both contain the same type: car PLUS I have overloaded the hashCode and equals of car
carList has 1106 items
documentList has 88 items
I would like to remove the 88 items of documentList from the carList.
(simple math: 1106-88=1018)
By doing this:
(1)
this.carList.removeAll(documentList);
the carList.size() = 1013 (?!?!)by doing this:
(2)
             for (int x=carList.size()-1; x>=0; x--)
                  Car cx = (Car) carList.get(x);
                  for (int i=documentList.size()-1; i>=0; i--)
                       Car ci = (Car) documentList.get(i);
                       if (cx.equals(ci))
                            carList.remove(x);
                            documentList.remove(i);
                            break;
             }I get 1018 (correct)
Question: Why am I getting the wrong result in option 1? (once again, I have overloaded the hashCode and equals of car)

Answer 1

I am going to guess - and it is a guess - that it is down to the way the removeAll() method works 'under the covers' so to speak. Like you, I cannot think of any reason why the results should differ given that I would expect the equals() method - which you overrode - that would be called upon most. Sorry I cannot help any further.