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https://issues.apache.org/jira/browse/LUCENE-460?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13712635#comment-13712635
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Dawid Weiss commented on LUCENE-460:
------------------------------------
There isn't really much to understand, it's pretty simple.
{code}
h = (h<<1) | (h >>> 31); // rotate left
{code}
These are rotation bitshifts -- there is no operator for it in Java. There's
actually an intrinsic for this (Integer.rotateLeft and rotateRight).
Now which sequence of operations -- the one above or IntelliJ generated one --
is "better" is a difficult question to answer -- depends how many collisions
you actually get for real life include/exclude pairs. I doubt there'll be many.
Multiplications used to be much smaller than bitshifts and logical operations
so the first version is probably historically motivated (as being faster).
> hashCode improvements
> ---------------------
>
> Key: LUCENE-460
> URL: https://issues.apache.org/jira/browse/LUCENE-460
> Project: Lucene - Core
> Issue Type: Improvement
> Components: core/search
> Reporter: Yonik Seeley
> Assignee: Yonik Seeley
> Priority: Minor
>
> It would be nice for all Query classes to implement hashCode and equals to
> enable them to be used as keys when caching.
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