commons-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Henri Yandell (JIRA)" <j...@apache.org>
Subject [jira] Commented: (COLLECTIONS-246) LoopingListIterator behaves unexpected on next and previous mixed
Date Sun, 06 Apr 2008 02:41:25 GMT

    [ https://issues.apache.org/jira/browse/COLLECTIONS-246?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12586084#action_12586084
] 

Henri Yandell commented on COLLECTIONS-246:
-------------------------------------------

Can you restate your failing test? Looking at the description, I was taking it as:

{code:java}
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! 
{code}

Your statement here is incorrect - the answer should be 0 not 2. This is the base of your
misunderstanding - you are not "on 0", you are "before 0". I think that's a part of the java.util.Iterator
concept; and that we shouldn't implement an alternative to java.util.Iterator as it would
lead to having to write lots of code.

> 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.

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.


Mime
View raw message