Re: Suggestion for overriding equals() method

[Chris Hostetter <ho...@fucit.org>]

Fuxiang: thank you for your email about this.

I've filed this in our jira tracker -- if you have a patch you'd like to 
provide to help move this issue forward, please attach there...

https://issues.apache.org/jira/browse/LUCENE-6744
https://wiki.apache.org/lucene-java/HowToContribute



: Date: Sun, 12 Jul 2015 14:29:02 +0800
: From: Fuxiang Chen <fc...@cse.ust.hk>
: Reply-To: dev@lucene.apache.org
: To: dev@lucene.apache.org
: Subject: Suggestion for overriding equals() method
: 
: Dear Developers,
: 
: 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.
: 
: Do kindly consider making the suggestion for the changes.
: 
: Reference:
: [1] http://stackoverflow.com/questions/19642810 (based on the latest
: highest answer)
: [2] http://docs.oracle.com/javase/7/docs/api/java/util/Objects.html (based
: on [1])
: [3] http://stackoverflow.com/questions/7132649 (based on the highest answer)
: 
: Thanks!
: 
: -- 
: Warmest Regards,
:     Fuxiang
: 

-Hoss
http://www.lucidworks.com/

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