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From "Frank Hefter (JIRA)" <j...@apache.org>
Subject [jira] Commented: (COLLECTIONS-246) LoopingListIterator behaves unexpected on next and previous mixed
Date Wed, 02 Apr 2008 08:34:25 GMT

    [ https://issues.apache.org/jira/browse/COLLECTIONS-246?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12584459#action_12584459
] 

Frank Hefter commented on COLLECTIONS-246:
------------------------------------------

For my opinion this test case is to simple and can't be compared with the more complex swap
over at the beginning and the end of this LoopingList (thats the error I ment btw. !).

You simply take a java.util.Iterator test. But this ignores the abilities of this class comletely.

Again, please give me test cases that are better than mine. 

Also your test works with this fix, too. So it is an iterator? Right?

Just for the case: I don't care about the implementation. Just my tests have to apply.
So we can focus on the tests and make them more complexe. 

Is there a LoopIterator pattern somewhere? If not: Let's create it !

> LoopingListIterator behaves unexpected on next and previous mixed
> -----------------------------------------------------------------
>
>                 Key: COLLECTIONS-246
>                 URL: https://issues.apache.org/jira/browse/COLLECTIONS-246
>             Project: Commons Collections
>          Issue Type: Bug
>          Components: Iterator
>    Affects Versions: 3.2
>         Environment: JDK 1.4.2_12 
> Common Collections 3.2
>            Reporter: Frank Hefter
>            Priority: Blocker
>             Fix For: 3.3
>
>         Attachments: LoopingListIterator.java, LoopingListIterator.java, LoopingListIteratorTest.java
>
>
> Using ArrayList as the backing list. 
> This combination at least returns unexpected results as you can see in the testcase below.
> I used this for a list navigator in a web frontend and had trouble with users.
> I suspect java.util.AbstrList$ListItr (role of "cursor" var seems to be wrong implemented
) to cause this problem. If so maybe we have to implement it in a different way.
> Testcase (it runs without hassle but the comments show whats wrong):
> -------------------------------------------
> import java.util.ArrayList;
> import junit.framework.TestCase;
> import org.apache.commons.collections.iterators.LoopingListIterator;
> public class SelectionControllerTest extends TestCase {
>     public void testSelectorForApache() {
>         ArrayList al = new ArrayList();
>         al.add("0"); al.add("1"); al.add("2");
>         LoopingListIterator it = new  LoopingListIterator(al);
>         assertEquals("0", it.next()); // This is OK
>         // here I am on "0"
>         assertEquals("0", it.previous()); // Wrong ! This should be 2!
>         //      here I am on "0" too! This is wrong.
>         assertEquals("2", it.previous());
>         assertEquals("1", it.previous());
>         assertEquals("0", it.previous());
>         assertEquals("2", it.previous());
>         // here I am on "2" 
>         assertEquals("2", it.next()); // Wrong ! This should be 0!
>         // here I am on "2" too! This is wrong.
>         assertEquals("0", it.next()); 
>         assertEquals("1", it.next());
>         // here I am on "1"         
>         assertEquals("1", it.previous()); // Wrong ! This should be 0!
>     }
> }
> -------------------------------------------
> Thanks for your help.

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