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https://issues.apache.org/jira/browse/COLLECTIONS-310?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13580284#comment-13580284
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Thomas Vahrst edited comment on COLLECTIONS-310 at 2/17/13 8:53 PM:
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I am trying to create a sublist implementation which conforms to the required
functions. The first attachement (SetUniqueListTest.patch) contains many new
testcases for sublist, checking this functions.
I implemented two possible solutions, more of that in the following posts (in
the next days). During the coding I realized a further problem concerning
ListIterator. ListIterator supports add/set/remove functionality, which means,
that a ListIterator based on a sublist needs the corresponding sublist
behavior. And ListIterator may start at a specified index, so this means, that
a ListIterator with index > 0 based on a SetUniqueList itself is a subList of
the underlying SetUniqueList - with all the necessary behavior.
So for the first iteration on this issue, I ommited these tests. I will
provided them later...
was (Author: t.vahrst):
I am trying to create a sublist implementation which conforms to the
required functions. The first attachement (SetUniqueListTest.patch) contains
many new testcases for sublist, checking this functions.
I implemented two possible solutions, more of that in the next posts. During
the coding I realized a further problem concerning ListIterator. ListIterator
supports add/set/remove functionality, which means, that a ListIterator based
on a sublist needs the corresponding sublist behavior. And ListIterator may
start at a specified index, so this means, that a ListIterator with index > 0
based on a SetUniqueList itself is a subList of the underlying SetUniqueList -
with all the necessary behavior.
So for the first iteration on this issue, I ommited these tests. I will
provided them later...
> Modifications of a SetUniqueList.subList() invalidate the parent list
> ---------------------------------------------------------------------
>
> Key: COLLECTIONS-310
> URL: https://issues.apache.org/jira/browse/COLLECTIONS-310
> Project: Commons Collections
> Issue Type: Bug
> Components: List
> Affects Versions: 3.2, Nightly Builds
> Reporter: Christian Semrau
> Priority: Minor
> Fix For: 4.0
>
> Attachments: SetUniqueListTest.patch
>
>
> The List returned by SetUniqueList.subList() is again a SetUniqueList. The
> contract for List.subList() says that the returned list supports all the
> operations of the parent list, and it is backed by the parent list.
> We have a SetUniqueList uniqueList equal to {"Hello", "World"}. We get a
> subList containing the last element. Now we add the element "Hello",
> contained in the uniqueList but not in the subList, to the subList.
> What should happen?
> Should the subList behave like a SetUniqueList and add the element - meaning
> that it changes position in the uniqueList because at the old place it gets
> removed, so now uniqueList equals {"World", "Hello"} (which fails)?
> Or should the element not be added, because it is already contained in the
> parent list, thereby violating the SetUniqueList-ness of the subList (which
> fails)?
> I prefer the former behaviour, because modifications should only be made
> through the subList and not through the parent list (as explained in
> List.subList()).
> What should happen if we replace (using set) the subList element "World" with
> "Hello" instead of adding an element?
> The subList should contain only "Hello", and for the parent list, the old
> element 0 (now a duplicate of the just set element 1) should be removed
> (which fails).
> And of course the parent list should know what happens to it (specifically,
> its uniqueness Set) (which fails in the current snapshot).
> public void testSubListAddNew() {
> List uniqueList = SetUniqueList.decorate(new ArrayList());
> uniqueList.add("Hello");
> uniqueList.add("World");
> List subList = uniqueList.subList(1, 2);
> subList.add("Goodbye");
> List expectedSubList = Arrays.asList(new Object[] { "World",
> "Goodbye" });
> List expectedParentList = Arrays.asList(new Object[] { "Hello",
> "World", "Goodbye" });
> assertEquals(expectedSubList, subList);
> assertEquals(expectedParentList, uniqueList);
> assertTrue(uniqueList.contains("Goodbye")); // fails
> }
> public void testSubListAddDuplicate() {
> List uniqueList = SetUniqueList.decorate(new ArrayList());
> uniqueList.add("Hello");
> uniqueList.add("World");
> List subList = uniqueList.subList(1, 2);
> subList.add("Hello");
> List expectedSubList = Arrays.asList(new Object[] { "World",
> "Hello" });
> List expectedParentList = Arrays.asList(new Object[] { "World",
> "Hello" });
> assertEquals(expectedSubList, subList);
> assertEquals(expectedParentList, uniqueList); // fails
> }
> public void testSubListSetDuplicate() {
> List uniqueList = SetUniqueList.decorate(new ArrayList());
> uniqueList.add("Hello");
> uniqueList.add("World");
> List subList = uniqueList.subList(1, 2);
> subList.set(0, "Hello");
> List expectedSubList = Arrays.asList(new Object[] { "Hello" });
> List expectedParentList = Arrays.asList(new Object[] { "Hello"
> });
> assertEquals(expectedSubList, subList);
> assertEquals(expectedParentList, uniqueList); // fails
> }
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