141-java-refactoring-with-modern-features - Claude MCP Skill

# Modern Java Development Guidelines (Java 8+)

Identify and apply modern Java (Java 8+) refactoring opportunities to improve readability, maintainability, and performance.

**What is covered in this Skill?**

- Lambda expressions and method references (over anonymous classes)
- Stream API for declarative collection processing
- `Optional` for null-safe APIs
- `java.time` API (replacing `Date`/`Calendar`)
- Default interface methods, `var` type inference
- Unmodifiable collection factory methods (`List.of()`, `Set.of()`, `Map.of()`)
- Text blocks for multi-line strings
- Java 25 Flexible Constructor Bodies (JEP 513)
- Java 25 Module Import Declarations (JEP 511)

**Scope:** The reference is organized by examples (good/bad code patterns) for each core area. Apply recommendations based on applicable examples.

## Constraints

Before applying any modern Java refactoring, ensure the project compiles. If compilation fails, stop immediately — do not proceed until the project compiles successfully. After applying improvements, run full verification.

- **MANDATORY**: Run `./mvnw compile` or `mvn compile` before applying any changes
- **SAFETY**: If compilation fails, stop immediately — do not proceed until the project compiles successfully
- **VERIFY**: Run `./mvnw clean verify` or `mvn clean verify` after applying improvements
- **BEFORE APPLYING**: Read the reference for detailed good/bad examples, constraints, and safeguards for each modern Java feature
- **EDGE CASE**: If request scope is ambiguous, stop and ask a clarifying question before applying changes
- **EDGE CASE**: If required inputs, files, or tooling are missing, report what is missing and ask whether to proceed with setup guidance

## When to use this skill

- Review Java code for modern Java development
- Apply best practices for modern Java development in Java code

## Workflow

1. **Compile project before modernization**

Run `./mvnw compile` or `mvn compile` and stop immediately if compilation fails.

2. **Read modern-Java reference and identify candidates**

Read `references/141-java-refactoring-with-modern-features.md` and identify high-value opportunities to adopt modern Java features.

3. **Apply modern Java refactorings**

Refactor incrementally using appropriate language/library features while preserving behavior and readability.

4. **Verify with full build**

Run `./mvnw clean verify` or `mvn clean verify` after applying improvements.

## Reference

For detailed guidance, examples, and constraints, see [references/141-java-refactoring-with-modern-features.md](references/141-java-refactoring-with-modern-features.md).