On Fri, 4 Aug 2023 15:01:51 GMT, Pavel Rappo <[email protected]> wrote:
>> src/java.base/share/classes/sun/security/x509/PolicyInformation.java line
>> 140:
>>
>>> 138: @Override
>>> 139: public int hashCode() {
>>> 140: return Objects.hash(policyIdentifier, policyQualifiers);
>>
>> What is the criteria for changing the hashCode() impl? It seems that you
>> change some and not others. With the many hashCode() impls (e.g.
>> Objects.hash(), Arrays.hashCode()), I wonder why this and not that.
>
> Whether I suggest changing hashCode or not depends on multiple criteria, of
> which these two are the most important:
>
> * Is the value specified or relied upon?
> * Does it need to be performant?
>
> If the answer to both of these is "NO", I might refactor hashCode. One
> unintended side effect, is that sometimes such a refactoring improves
> hashCode quality (think: perfect hashing) almost for free.
>
> If you have concerns on particular refactorings, I'd be happy to discuss them.
I would add to that list that I think it is really important any change to the
`hashCode` impl doesn't break the equals/hashCode contract, so it's important
to look at the `equals` implementation in conjunction with any changes to
`hashCode`, mostly to ensure 2 equal objects continue to have the same hash
code. It is also important to question any oddity about the `hashCode` impl,
like I did for DESKey and try to understand why it may have been implemented
that way, such as skipping the first byte.
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PR Review Comment: https://git.openjdk.org/jdk/pull/14738#discussion_r1284801790
