RFR: 8371953: Document null handling in core reflection APIs [v3]

[David Holmes]

On Sun, 16 Nov 2025 08:45:38 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> Chen Liang 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 11 additional commits since the last revision:
>> 
>>  - From review
>>  - Merge branch 'master' of https://github.com/openjdk/jdk into fix/core-reflection-null-checks
>>  - Rephrase for parameterTypes contains null
>>  - Rename tests to be more specific
>>  - Split annotated type new checks to another patch
>>  - Redundant
>>  - Test and more fixes
>>  - Copyright years
>>  - Testing
>>  - Merge branch 'master' of https://github.com/openjdk/jdk into fix/core-reflection-null-checks
>>  - ... and 1 more: https://git.openjdk.org/jdk/compare/edfda06d...51ef5789
>
> src/java.base/share/classes/java/lang/Class.java line 3839:
> 
>> 3837:      */
>> 3838:     public boolean isNestmateOf(Class<?> c) {
>> 3839:         Objects.requireNonNull(c);
> 
> So the behavior change here is calling isNestmateOf(null) on a class object for a primitive or array class will throw NPE when it didn't throw it previously.  Technically an incompatible change but I agree it's in the weeds when it comes to impact.

A null check was not considered necessary for this API. If you ask `c.isNestMateOf(null)` the answer is `false`. We chose not to report you had "asked a stupid question".

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PR Review Comment: https://git.openjdk.org/jdk/pull/28336#discussion_r2540733026