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https://issues.apache.org/jira/browse/COLLECTIONS-878?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18030451#comment-18030451
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Gary D. Gregory commented on COLLECTIONS-878:
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[~safronovms]
Please see my comment in the PR.
> Wrong capacity calculation leads to extra resize in MapUtils.invertMap
> ----------------------------------------------------------------------
>
> Key: COLLECTIONS-878
> URL: https://issues.apache.org/jira/browse/COLLECTIONS-878
> Project: Commons Collections
> Issue Type: Improvement
> Components: Map
> Environment: Doesn't matter
> Reporter: Safronov Maxim
> Assignee: Gary D. Gregory
> Priority: Trivial
> Labels: easyfix, performance
>
> MapUtils.invertMap create map with the same size via HashMap constructor with
> wrong capacity parameter. The capacity must be calculated as in new static
> factory method HashMap.newHashMap (since 19). Old size must be divided to
> load factor, in our case DEFAULT_LOAD_FACTOR 0.75 that casted to double.
> Otherwise we have 50% probability that our map will be extra resized during
> insertion of inverted entries. Expensive operation.
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