Re: Collection implementations and fail-fast iterator problems.
Roedy Green wrote:
On Fri, 02 Nov 2007 14:06:09 -0700, Daniel Pitts
<newsgroup.spamfilter@virtualinfinity.net> wrote, quoted or indirectly
quoted someone who said :
I'd like to avoid having to keep track of "to-be-deleted" and
"to-be-added" elements, but I don't see an elegant way to handle both
those cases without getting a ConcurrentModificationError.
see http://mindprod.com/jgloss/iterator.html#REMOVE
The problem is that the element to remove isn't necessarily the element
that the iterator is pointing to. For example.
class ItemHolder {
Collection<Item> items;
public void doAllSomething() {
for (Item item: items) {
item.doSomething();
}
}
class Item {
ItemHolder parent;
public void doSomething() {
for (Item item: parent.items) {
item.affectBy(this);
if (item.shouldBeRemovedNow()) {
parent.items.remove(item);
}
}
if (shouldAddNewItems()) {
parent.items.add(createNewItem());
}
}
}
This is the gist of what happens. As you can see, there are multiple
iterators to deal with.
--
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