Bug in ArrayList iterator

[Paul Sandoz]

On Jan 7, 2015, at 10:45 AM, Remi Forax <forax at univ-mlv.fr> wrote:

> A simple Java question, what this code does ?
> 
>  ArrayList<String> list = new ArrayList<>();
>  list.add("foo");
>  list.add("bar");
>  for(String s: list) {
>    list.remove(s);
>  }
> 
> :(
> 

We could improve the best-effort basis by which ConcurrentModificationException is thrown by snapshotting the collection size on construction of the iterator (at the expense of an extra field, but that might pack into a spare 4 bytes due to alignment at least on 64 bits IIUC).

Paul.

> Rémi
> tip: the bug lies in ArrayList.Itr.hasNext() (and AbstractList.Itr.hasNext()).
>