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From "Niall Pemberton (JIRA)" <j...@apache.org>
Subject [jira] Updated: (LANG-575) HashCodeBuilder reflectionAppend creates unnecessary copy of excludeFields
Date Thu, 25 Feb 2010 19:52:28 GMT

     [ https://issues.apache.org/jira/browse/LANG-575?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Niall Pemberton updated LANG-575:
---------------------------------

    Fix Version/s:     (was: 3.0)
                   2.5

> HashCodeBuilder reflectionAppend creates unnecessary copy of excludeFields
> --------------------------------------------------------------------------
>
>                 Key: LANG-575
>                 URL: https://issues.apache.org/jira/browse/LANG-575
>             Project: Commons Lang
>          Issue Type: Bug
>          Components: lang.builder.*
>    Affects Versions: 2.4
>         Environment: Sun Java JDK 1.6.0_17
>            Reporter: Anthony Whitford
>             Fix For: 2.5
>
>
> See http://svn.apache.org/viewvc/commons/proper/lang/trunk/src/java/org/apache/commons/lang3/builder/HashCodeBuilder.java?view=markup
> Please review the implementation for *reflectionAppend* (lines 174 to 202)...  Specifically,
see line 182:
> {code}
> List<String> excludedFieldList = excludeFields != null ? Arrays.asList(excludeFields)
: Collections.<String>emptyList();
> {code}
> Note that if you are in the habit of passing in a String array for excluding fields ({{String[]
excludeFields}}) -- which is a best practice when using Hibernate (to skip primary keys ({{@id}})
and version fields ({{@version}}) that change upon persistence) -- _EVERY TIME_ the _hashCode_
is calculated, an _ArrayList_ is being created -- generating fodder for the garbage collector.
> I thought I might get around this by passing a {{Collection<String>}} instead of
a {{String[]}}, but ironically the implementation of the {{reflectionHashCode(Object object,
Collection<String> excludeFields)}} (see lines 475 to 477), for example, transforms
the {{Collection<String>}} into a {{String[]}} only to have it transformed internally
into a temporary {{ArrayList<String>}}.
> I would expect the implementation to use and read what is submitted, whether that is
a {{String[]}} or a {{Collection<String>}}.  I don't think it needs to create another
copy just to have a convenient {{contains}} method.  Efficiency is important, especially in
the event of rehashing.

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