RFR: 8350880: (zipfs) Add support for read-only zip file systems [v12]

[Jaikiran Pai]

On Wed, 21 May 2025 23:30:18 GMT, David Beaumont <duke at openjdk.org> wrote:

>> Adding read-only support to ZipFileSystem.
>> 
>> The new `accessMode` environment property allows for readOnly and readWrite values, and ensures that the requested mode is consistent with what's returned.
>> 
>> This involved a little refactoring to ensure that "read only" state was set initially and only unset at the end of initialization if appropriate.
>> 
>> By making 2 methods return values (rather than silently set non-final fields as a side effect) it's now clear in what order fields are initialized and which are final (sadly there are still non-final fields, but only a split of this class into two types can fix that, since determining multi-jar support requires reading the file system).
>
> David Beaumont has updated the pull request incrementally with one additional commit since the last revision:
> 
>   More tweaking...

This looks good to me. I would have prefered not changing the intial value of a the `readOnly` field to `true`, because that would mean one less thing to be concerned about. However, I am not too sure if it makes a practical difference. So what you have I think is OK. I'll think about it a bit more later and if anything shows up, I think we can address it. 

I think this enhancement deserves a release note, so I have added that label to the JBS issue. Instructions for creating a release note are available here https://openjdk.org/guide/#release-notes.

Thank you David for being patient with the back and forth discussions and reviews. Please wait for Alan and Lance to have a chance to look at the final state of this PR before integrating.

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Marked as reviewed by jpai (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/25178#pullrequestreview-2864523197