RFR: 8366517: `DateFormatSymbols(Locale)` throws NPE if `Locale` argument is null [v3]

[Naoto Sato]

On Wed, 3 Sep 2025 16:01:01 GMT, Justin Lu <jlu at openjdk.org> wrote:

>> Right. Added the explicit null check. (and a test case)
>
> If we are adding an explicit check to the ctor, might we also take this opportunity to add the check to the related 1-arg factory method?

Indeed. Also did the same for `DecimalFormatSymbols`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/27060#discussion_r2319613332