On Fri, 4 Aug 2023 15:01:51 GMT, Pavel Rappo <pra...@openjdk.org> 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. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/14738#discussion_r1284801790