[
https://issues.apache.org/jira/browse/LUCENE-6744?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14701688#comment-14701688
]
Edward Ribeiro commented on LUCENE-6744:
----------------------------------------
My two cents: I have always preferred to use {{instanceof}}, but was unaware of
the potential problems and inconsistencies of using it. :( So, for stir up a
little bit of discussion, I would like let you with two SO links that discuss
this issue in depth:
http://stackoverflow.com/questions/596462/any-reason-to-prefer-getclass-over-instanceof-when-generating-equals
http://stackoverflow.com/questions/27581/what-issues-should-be-considered-when-overriding-equals-and-hashcode-in-java/32223#32223
Best,
eddie
> equals methods should compare classes directly, not use instanceof
> ------------------------------------------------------------------
>
> Key: LUCENE-6744
> URL: https://issues.apache.org/jira/browse/LUCENE-6744
> Project: Lucene - Core
> Issue Type: Bug
> Reporter: Hoss Man
> Labels: newdev
>
> from a 2015-07-12 email to the dev list from Fuxiang Chen...
> {noformat}
> We have found some inconsistencies in the overriding of the equals() method
> in some files with respect to the conforming to the contract structure
> based on the Java Specification.
> Affected files:
> 1) ConstValueSource.java
> 2) DoubleConstValueSource.java
> 3) FixedBitSet.java
> 4) GeohashFunction.java
> 5) LongBitSet.java
> 6) SpanNearQuery.java
> 7) StringDistanceFunction.java
> 8) ValueSourceRangeFilter.java
> 9) VectorDistanceFunction.java
> The above files all uses instanceof in the overridden equals() method in
> comparing two objects.
> According to the Java Specification, the equals() method must be reflexive,
> symmetric, transitive and consistent. In the case of symmetric, it is
> stated that x.equals(y) should return true if and only if y.equals(x)
> returns true. Using instanceof is asymmetric and is not a valid symmetric
> contract.
> A more preferred way will be to compare the classes instead. i.e. if
> (this.getClass() != o.getClass()).
> However, if compiling the source code using JDK 7 and above, and if
> developers still prefer to use instanceof, you can make use of the static
> methods of Objects such as Objects.equals(this.id, that.id). (Making use of
> the static methods of Objects is currently absent in the methods.) It will
> be easier to override the equals() method and will ensure that the
> overridden equals() method will fulfill the contract rules.
> {noformat}
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
