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https://issues.apache.org/jira/browse/LANG-1499?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17023886#comment-17023886
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Zhiqiang Zang commented on LANG-1499:
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[~sebb] Thank you for your comments. Thank you for pointing out some
inconsistency between Javadoc and code, which should be inspected, too. I want
to share more findings such that this issue makes more sense.
equals() method should be able to return true when comparing two different
classes sharing a common superclass, such as LinkedList and ArrayList. Actually
Java built-in equals() method supports this case.
The code for EqualsBuilder.reflectionEquals() does check if one class is a
superclass of the other but it simply returns false for all other cases, which
is the cause of the issue.
[https://commons.apache.org/proper/commons-lang/xref/org/apache/commons/lang3/builder/EqualsBuilder.html#L522]
One potential fix could be to have another else if branch to check if two
classes share a common superclass.
> Equals transitivity is violated in EqualsBuilder
> ------------------------------------------------
>
> Key: LANG-1499
> URL: https://issues.apache.org/jira/browse/LANG-1499
> Project: Commons Lang
> Issue Type: Bug
> Components: lang.builder.*
> Affects Versions: 3.9
> Environment: Ubuntu 18.04
> JDK 1.8.0_221
> Commons Lang 3.9-RC2
> JUnit 5.4
> Reporter: Zhiqiang Zang
> Priority: Major
> Labels: Equals(), EqualsBuilder, transitivity
> Attachments: EqualsTransitivityTest.java
>
>
> EqualsBuilder.reflectionEquals() does not hold transitivity when comparing
> two subclasses extending a common superclass. For example:
> Given that both class D and E are subclasses of class C, C == D and C == E
> should imply D == E. However EqualsBuilder.reflectionEquals(D, E) returns
> *false* when both EqualsBuilder.reflectionEquals(C, D) and
> EqualsBuilder.reflectionEquals(C, E) return true.
> A junit test is provided as attachment.
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