[jira] Updated: (LANG-575) HashCodeBuilder reflectionAppend creates unnecessary copy of excludeFields

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

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

Henri Yandell updated LANG-575:
-------------------------------

    Fix Version/s: 3.0

Definitely hoping to challenge the builder code before 3.0 is released. Its got the most duplication and the most JIRA items open.

Thanks for both of your optimization suggestions.

> 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: 3.0
>
>
> 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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