RFR: 8268764: Use Long.hashCode() instead of int-cast where applicable [v2]

[Kevin Walls]

On Wed, 30 Jun 2021 11:49:51 GMT, Сергей Цыпанов <github.com+10835776+stsypanov at openjdk.org> wrote:

>> In some JDK classes there's still the following hashCode() implementation:
>> 
>> long objNum;
>> 
>> public int hashCode() {
>>     return (int) objNum;
>> }
>> 
>> This outdated expression should be replaced with Long.hashCode(long) as it
>> 
>> - uses all bits of the original value, does not discard any information upfront. For example, depending on how you are generating the IDs, the upper bits could change more frequently (or the opposite).
>> 
>> - does not introduce any bias towards values with more ones (zeros), as it would be the case if the two halves were combined with an OR (AND) operation.
>> 
>> See https://stackoverflow.com/a/4045083
>> 
>> This is related to https://github.com/openjdk/jdk/pull/4309
>
> Сергей Цыпанов has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:
> 
>  - Merge branch 'master' into 8268764
>  - 8268764: Use Long.hashCode() instead of int-cast where applicable

The changes look good to me, we have done the same thing elsewhere.  This changes things in different functional areas, which is maybe unusual, but seems fine for a small change as long as nobody objects.

Some of the files also need a (C) year update.

-------------

PR: https://git.openjdk.java.net/jdk/pull/4491