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https://issues.apache.org/jira/browse/LANG-786?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13479161#comment-13479161
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Dmitry Katsubo commented on LANG-786:
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I think there is still area for improvement: [line 192 of
CharSequenceUtils()|http://svn.apache.org/viewvc/commons/proper/lang/trunk/src/main/java/org/apache/commons/lang3/CharSequenceUtils.java?revision=1199894&view=markup#l192]
reads
{{TODO: Implement rather than convert to String}}
In my case I have {{CharSequence}} that implements a "lazy" string, and
{{toString()}} implementation is very expensive plus can potentially cause OOM.
Thus {{CharSequenceUtils.regionMatches()}} should really do char-by-char
comparison, leaving the optimization to underlying {{CharSequence}}
implementation.
> StringUtils equals() relies on undefined behavior
> -------------------------------------------------
>
> Key: LANG-786
> URL: https://issues.apache.org/jira/browse/LANG-786
> Project: Commons Lang
> Issue Type: Bug
> Components: lang.*
> Affects Versions: 3.x
> Environment: java version "1.7.0_02"
> Java(TM) SE Runtime Environment (build 1.7.0_02-b13)
> Java HotSpot(TM) 64-Bit Server VM (build 22.0-b10, mixed mode)
> Fedora 15 AMD64
> Reporter: Daniel Trebbien
> Labels: StringUtils
> Fix For: 3.2
>
> Attachments: equals.patch
>
>
> Since the {{java.lang.CharSequence}} class was first introduced in 1.4, the
> JavaDoc block has contained the following note:
> {quote}
> This interface does not refine the general contracts of the equals and
> hashCode methods. The result of comparing two objects that implement
> CharSequence is therefore, in general, undefined. Each object may be
> implemented by a different class, and there is no guarantee that each class
> will be capable of testing its instances for equality with those of the other.
> {quote}
> When the signature of the StringUtils equals() method was changed from
> {{equals(String, String)}} to {{equals(CharSequence, CharSequence)}} in
> R920543, the implementation still relied on calling
> CharSequence#equals(Object) even though, in general, the result is undefined.
> One example where {{equals(Object)}} returns {{false}} even though, as
> CharSequences, two objects represent equal sequences is when one object is an
> instance of {{javax.lang.model.element.Name}} and the other object is a
> String.
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