[jira] Closed: (COLLECTIONS-302) CollectionUtils.subtract() should not use ArrayList to improve speed

["Henri Yandell (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/COLLECTIONS-302?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Henri Yandell closed COLLECTIONS-302.
-------------------------------------

    Resolution: Won't Fix

No worries - closing the issue as there's nothing major here to work on.

> CollectionUtils.subtract() should not use ArrayList to improve speed
> --------------------------------------------------------------------
>
>                 Key: COLLECTIONS-302
>                 URL: https://issues.apache.org/jira/browse/COLLECTIONS-302
>             Project: Commons Collections
>          Issue Type: Improvement
>          Components: Collection
>            Reporter: Joachim Rudolph
>            Priority: Minor
>   Original Estimate: 2h
>  Remaining Estimate: 2h
>
> The implementation of version 3.2.1 is
> public static Collection subtract(final Collection a, final Collection b) {
>         ArrayList list = new ArrayList( a );
>         for (Iterator it = b.iterator(); it.hasNext();) {
>             list.remove(it.next());
>         }
>         return list;
>     }
> when a and b are large and similar the subtract implementation will call ArrayList.remove() frequently which copies a potentially large part of the list using system.arraycopy.
> Suggestion : use LinkedList ( at least for large lists )

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