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From "Frank hefter (JIRA)" <>
Subject [jira] Created: (COLLECTIONS-246) LoopingListIterator behaves unexpected on next and previous mixed
Date Tue, 20 Mar 2007 09:07:32 GMT
LoopingListIterator behaves unexpected on next and previous mixed

                 Key: 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

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",; // This is OK
        // here I am on "0"
        assertEquals("0", it.previous()); // Wrong ! This should be 3!
        //      here I am on "0" too! This wrong.
        assertEquals("2", it.previous());
        assertEquals("1", it.previous());
        assertEquals("0", it.previous());
        assertEquals("2", it.previous());
        // here I am on "2" 
        assertEquals("2",; // Wrong ! This should be 0!
        // here I am on "2" too! This wrong.
        // here I am on "1"         
        assertEquals("1", it.previous()); // Wrong ! This should be 0!

Thanks for your help.

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