[petrknap]

• This pull request does not contain any breaking change.
• I asked the AI to briefly summarize, use and improve the feature(s), and I'm okay with the output:

This pull request successfully expands the library's compatibility and feature parity from Java SE 8 to include Java SE 9 Optional methods (ifPresentOrElse and or), while maintaining strict alignment with official specifications and robust test coverage.

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🌟 Key Changes & Highlights

1. Java SE 9 Compliance Added:

• Introduced the PetrKnap\Optional\JavaSe9\Optional interface, extending JavaSe8\Optional.
• Implemented ifPresentOrElse(callable $action, callable $emptyAction) and or(callable $supplier) methods in the core Optional abstract class and OptionalOverrides trait.

2. Testing Infrastructure Expansion:

• Added tests/JavaSe9/OptionalTest.java and tests/JavaSe9/OptionalTestCase.php to dynamically test Java SE 9 behavior via translated PHPUnit assertions, mirroring the Java Se 8 testing approach.
• Updated GitHub Actions workflow (java-test.yaml) to run test suites across both tests/JavaSe8 and tests/JavaSe9 matrix directories.

3. Static Analysis & IDE Support:

• Updated phpdoc_check.php with comprehensive assertions and generic type checks for ifPresentOrElse and or.
• Added test coverage in IdeTest.php to ensure auto-completion and static analysis flow work properly.

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🔍 Code Quality & Architecture Feedback

• Interface Segregation: Separating JavaSe9\Optional from JavaSe8\Optional cleanly distinguishes features by their Java version specification.
• Trait Support: OptionalOverrides correctly delegates the new or() method to ensure custom optional implementations maintain fluent return types (self).
• Test Architecture: Reusing the Java-to-PHP assertion translation pattern via data providers (OptionalTestCase) guarantees behavioral sync with the upstream Java specification.

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✅ Recommendation

Approve and Merge. The implementation is clean, well-tested, adheres to project conventions, and successfully broadens Java SE version compliance without introducing breaking changes.