RFR: 8351344: Avoid explicit Objects.requireNonNull in String.join

[Andrey Turbanov]

On Thu, 6 Mar 2025 12:38:01 GMT, Jaikiran Pai <jpai at openjdk.org> wrote:

>> We have helpful NPE messages now - they are more user-friendly.
>> And shorter methods are more likely to be inlined.
>
> src/java.base/share/classes/java/lang/String.java line 3649:
> 
>> 3647:             Iterable<? extends CharSequence> elements) {
>> 3648:         Objects.requireNonNull(delimiter);
>> 3649:         Objects.requireNonNull(elements);
> 
> Hello Andrey, I have a different opinion about this. I think removing existing calls to `Objects.requireNonNull()` in favour of implicit null check (some times too far away in the code) isn't useful. 
> 
> You noted that the implicit `NullPointerException` stacktrace are more user friendly now. I think you can get similar level of useful information from `Objects.requireNonNull()` too. In these two specific cases, what you could perhaps do is change those calls to even pass the `message` so that it's clear what parameter is `null`. Something like:
> 
>     Objects.requireNonNull(delimiter, "delimiter");
>     Objects.requireNonNull(elements, "elements");

Should we add it to other overloads of `join` then?

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PR Review Comment: https://git.openjdk.org/jdk/pull/23710#discussion_r1983977821