How to fix ConcurrentModificationException, removing item from arrayList?

Question

I would like to delete an item from my arrayList while iterating through it, and the ArrayList has a type class Members. I have read multiple examples of how to fix this problem however none have worked, the ConcurrentModificationException is still thrown.

Iterator<Members> itr = members.iterator();
while (itr.hasNext()) {
  Members foundMember = itr.next();
  if (foundMember.equals(member)){
    itr.remove();
  }
}

`members.removeIf(m -> m.equals(member));` would be an easier way to do this. — Andy Turner, May 07 '19 at 11:11
This code would not throw a CME in and of itself: this is the correct way to remove whilst iterating. `members` must be updated elsewhere (or this code is invoked from multiple threads). — Andy Turner, May 07 '19 at 11:12

score 0 · Answer 1 · answered May 08 '19 at 15:46

0

The solution i ended up with was, using a CopyOnWriteArrayList, instead of an ArrayList nad using the remove(); methode.

answered May 08 '19 at 15:46

Camille Sandidge

41
3

JavaMan · Answer 2 · 2019-05-07T12:09:02.697

-1

EDIT of course my first solution was incorrect facepalm as suggested above, ".removeIf" is most likely the simplest solution.

just use a "normal" for loop (I think that should work, pls. take a look at this, btw. an "enhanced for loop" will not work.

List<Member> list1 = new ArrayList<>();
List<Member> list2 = new ArrayList<>(list1);
for (int i = 0; i < list1.size(); i++) {
  Member member = list1.get(i);
  ...
  list2.remove(member);
}
list1 = list2;

edited May 07 '19 at 12:09

answered May 07 '19 at 11:22

JavaMan

1,142
12
22

3

You will skip the member at the next index though – Benjamin Urquhart May 07 '19 at 11:42

How to fix ConcurrentModificationException, removing item from arrayList?

2 Answers2