[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 11 Optional::isEmpty() into the PHP implementation. It adds the corresponding interface specification, updates the base Optional class, adds comprehensive Java-to-PHP test coverage for Java SE 11, and updates documentation (README.md and GitHub actions matrix).

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Detailed Code & Diff Review

1. Core Feature (src/JavaSe11/Optional.php & src/Optional.php)

• New Interface: Created PetrKnap\Optional\JavaSe11\Optional which extends JavaSe10\Optional and introduces isEmpty(): bool.
• Class Updates:
• PetrKnap\Optional\Optional now implements JavaSe11\Optional instead of JavaSe10\Optional.
• Implements isEmpty(): bool returning true when $this->value === null, perfectly aligning with Java's behavior.
• Includes a helpful developer note: @note do not use it internally, compare self::$value to null directly.

2. Testing & Parity (tests/JavaSe11/)

• Java Test File (tests/JavaSe11/OptionalTest.java): Added a new Java test checking that .isEmpty() returns false for present values and true for empty optional instances.
• PHP Test Case Adapter (tests/JavaSe11/OptionalTestCase.php): Extends JavaSe10\OptionalTestCase and dynamically loads the Java SE 11 test lines to ensure the PHP implementation matches Java semantics.
• Test Hierarchy Update (tests/JavaSe16/OptionalTestCase.php): Correctly refactored the inheritance chain from JavaSe10 to JavaSe11 (JavaSe16 tests now properly inherit from JavaSe11\OptionalTestCase).

3. CI/CD & Documentation (.github/workflows/java-test.yaml & README.md)

• GitHub Actions Matrix: Updated java-test.yaml to include a dedicated entry for se: 11 (lts: 11) to run validation tests.
• README: Added JavaSe11/OptionalTest.java to the list of specifications explicitly checking and describing the feature set, keeping documentation aligned with the code changes.

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Strengths & Best Practices

• Strict Specification Alignment: Following the pattern of mirroring Java SE specifications (JavaSe8, JavaSe9, JavaSe10, and now JavaSe11) ensures high reliability and predictable behavior.
• Automated Parity Tests: Reusing Java test assertions through reflection and automated translation strings (OptionalTestCase) guarantees that the PHP behavior will continue to match Java's standard library.
• Clean Commit Scope: The changes are focused, well-structured, and touch only what is necessary to introduce isEmpty().

Recommendation

• Status: Approved / Ready to Merge. The implementation is clean, properly tested, fully typed, and preserves backward compatibility while smoothly expanding Java API parity.