RFR: 8352969: G1: Improve testability of optional collections [v9]

[Guanqiang Han]

On Wed, 10 Sep 2025 15:20:20 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Guanqiang Han has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   fix a small error
>
> Looks good apart from that spacing in the test.

@tschatzl Thank you very much for your valuable comments. I’ve updated this PR accordingly. Could you please take another look.

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PR Comment: https://git.openjdk.org/jdk/pull/26880#issuecomment-3275566396