RFR: 8057113: (fs) Path should have a method to obtain the filename extension [v15]

[Roger Riggs]

On Wed, 27 Jul 2022 15:30:53 GMT, Brian Burkhalter <bpb at openjdk.org> wrote:

>> Resurrection of the proposal to add a method to obtain the filename extension originated in PR [2319](https://github.com/openjdk/jdk/pull/2319).
>
> Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8057113: Correct length 2 case; update test cases

Looks good.
As a default method, is there anything to say about when/if to implement for a specific file system.

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PR: https://git.openjdk.org/jdk/pull/8066