RFR: 8079136: Accessing a nested sublist leads to StackOverflowError

Pavel Rappo pavel.rappo at oracle.com
Wed May 6 09:12:33 UTC 2015


It looks like your change (I don't know whether it was intentional or not)
brings some more "fail-fast"-ness which is good! For instance, before the
change, this snippet:

    List<Integer> integers = new LinkedList<>();
    integers.addAll(Arrays.asList(0, 1));

    List<Integer> sublist = integers.subList(0, 2).subList(0, 2);

    System.out.print(" " + sublist.size());

would shamelessly produce: 2 2. But now it throws CME. Which is more expected I
believe. The reason is that now `checkForComodification` consults topmost list
rather than an immediate parent. Well to AbstractList's credit it's not a bug as
it falls into the category described in javadoc of java.util.List.subList:

    * The semantics of the list returned by this method become undefined if
    * the backing list (i.e., this list) is <i>structurally modified</i> in
    * any way other than via the returned list.  (Structural modifications are
    * those that change the size of this list, or otherwise perturb it in such
    * a fashion that iterations in progress may yield incorrect results.)

But still, it's a nice bonus for safety.


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