RFR: 8057113: (fs) Path should have a method to obtain the filename extension [v18]

[Stuart Marks]

On Mon, 1 Aug 2022 21:54:22 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: Remove API note

OK. I think the meta-requirements are that the behavior be well-specified, implemented correctly, have tests for all the edge cases, and ideally also have defensible behavior. (I was going to write "intuitive" behavior but that's an invitation for bikeshedding, which this change has already suffered from too much.)

I don't particularly care _which_ rule for special handling of `.` is used, as long as it meets the meta-requirements. I had proposed the "ignore all leading dots" rule because I thought it was simple, but I'm not beholden to this approach. If you (@bplb) prefer something different, then please go ahead with it.

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