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From "Sebb (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LANG-839) ArrayUtils removeElements methods use unnecessary HashSet
Date Tue, 09 Oct 2012 07:32:03 GMT

    [ https://issues.apache.org/jira/browse/LANG-839?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13472197#comment-13472197
] 

Sebb commented on LANG-839:
---------------------------

Thanks!

Note: this started because of the boxing warnings (adding int to HashSet).
I was looking for a way to eliminate them, and it occurred to me that the process seemed quite
inefficient.
                
> ArrayUtils removeElements methods use unnecessary HashSet
> ---------------------------------------------------------
>
>                 Key: LANG-839
>                 URL: https://issues.apache.org/jira/browse/LANG-839
>             Project: Commons Lang
>          Issue Type: Improvement
>          Components: lang.*
>    Affects Versions: 3.1
>            Reporter: Sebb
>            Priority: Minor
>             Fix For: 3.2
>
>         Attachments: LANG-839.patch
>
>
> The removeElements() methods use a HashSet to collect the indexes that need removing.
> This requires creating Integer objects for each index, and the HashSet then has to be
converted into an int[] array.
> It would be more efficient to store the entries in an actual int[] array.
> The maximum size of this is the length of the values array (or the length of the input
array if that is shorter).
> The array must be truncated before calling the private removeAll() method; this can be
done with Arrays.copyOf(x[], length).
> However, if the arrays are very large, and most of the values do not appear in the input,
this might result in using more memory than the HashSet implementation.

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