8359433: The final modifier on Windows L&F internal UI classes prevents extending them in apps

[mrserb]

Hi all,

This pull request contains a backport of commit 0d251968 from the openjdk/jdk26u repository.

The commit being backported was authored by Sergey Bylokhov on 1 Apr 2026 and had no reviewers.

The change is clean.

Thanks!

The reason for the fix (copied from mainline):

JDK-8352638 added final to public classes in java.desktop/windows including the Windows L&F package as a code consistency cleanup. This breaks applications that extend UI classes and they get IncompatibleClassChangeError at runtime.

Although this package is not part of the public API, we decided to remove the final modifier from all public and protected classes, as well as their inner classes in com.sun.java.swing.plaf.windows. Package-private classes, private inner classes, and the @Override annotations introduced by JDK-8352638 remain unchanged.

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• JDK-8359433 needs maintainer approval

Issue

• JDK-8359433: The final modifier on Windows L&F internal UI classes prevents extending them in apps (Bug - P3 - Approved)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk25u-dev.git pull/445/head:pull/445
$ git checkout pull/445

Update a local copy of the PR:
$ git checkout pull/445
$ git pull https://git.openjdk.org/jdk25u-dev.git pull/445/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 445

View PR using the GUI difftool:
$ git pr show -t 445

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk25u-dev/pull/445.diff

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[bridgekeeper]

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[openjdk]

@mrserb This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8359433: The final modifier on Windows L&F internal UI classes prevents extending them in apps

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At the time when this comment was updated there had been 1 new commit pushed to the master branch:

• be7cad4: 8374343: Fix SIGSEGV when lib/modules is unreadable

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[openjdk]

This backport pull request has now been updated with issue from the original commit.

[mrserb]

/approval request
Clean backport. The final modifier has been removed from internal UI Windows L&F classes.

[openjdk]

⚠️ @mrserb This change is now ready for you to apply for maintainer approval. This can be done directly in each associated issue or by using the /approval command.

[openjdk]

@mrserb
8359433: The approval request has been created successfully.

[mlbridge]

Webrevs

• 00: Full (22d5313d)