[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 introduces support for Java SE 10 and Java SE 16 specifications into the PHP Optional library. Specifically, it:

1. Adds JavaSe10\Optional interface containing the parameterless orElseThrow() method (which throws a NoSuchElementException by default).
2. Adds JavaSe16\Optional test harness and support for record-based equality checks.
3. Refactors the test setup (JavaSe8, JavaSe9, JavaSe10, JavaSe16) to use a clean matrix strategy in GitHub Actions (.github/workflows/java-test.yaml) and separates Java-to-PHP test translations cleanly.
4. Updates README.md to reference the new Java SE 10 and 16 compliance test suites.

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Detailed Code Review

1. Interface Evolution (src/JavaSe10/Optional.php)

• Addition: Introduces JavaSe10\Optional extending JavaSe9\Optional.
• Signature: public function orElseThrow(?callable $exceptionSupplier = null): mixed;
• PHPStan / Generics: The return type and conditional exception throwing are correctly documented using PHPStan templates and conditional throw types (@throws ($exceptionSupplier is null ? JavaSe8\NoSuchElementException : E)), matching the implementation already present in base Optional.

2. Test Suite & Java Compatibility Layer

• Java SE 10 Tests (tests/JavaSe10/OptionalTest.java): Properly tests parameterless orElseThrow() behavior for both present options and empty options.
• Java SE 16 & Records (tests/JavaSe16/OptionalTest.java & Record.php): Moves record-equality testing out of Java SE 8 (where records didn't exist natively) into the appropriate Java SE 16 context, maintaining accurate parity with Java's specification.
• CI Workflow (.github/workflows/java-test.yaml): Upgraded to actions/setup-java@v5 using Amazon Corretto across a matrix of Java versions (SE 8, 9, 10, and 16 mapped to appropriate LTS runtimes). This ensures robust verification against multiple Java target standards.

3. Documentation & Readme

• README.md: Updated to point to the new Java SE 10 and SE 16 test files, keeping documentation transparent about compliance targets.

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Recommendation

• Status: Approve ✅
• Reasoning: The changes are clean, strictly adhere to the project's goal of mirroring Java's Optional specifications across different language versions, improve the test architecture modularity, and pass all type-checking and structural conventions established in the library.