Use when you need to refactor Java code to adopt modern Java features (Java 8+) — including migrating anonymous classes to lambdas, replacing Iterator loops with Stream API, adopting Optional for null safety, switching from legacy Date/Calendar to java.time, using collection factory methods, applying text blocks, var inference, or leveraging Java 25 features like flexible constructor bodies and module import declarations. This should trigger for requests such as Review Java code for modern Java…
Use when you need to refactor Java code to adopt modern Java features (Java 8+) — including migrating anonymous classes to lambdas, replacing Iterator loops with Stream API, adopting Optional for null safety, switching from legacy Date/Calendar to java.time, using collection factory methods, applying text blocks, var inference, or leveraging Java 25 features like flexible constructor bodies and module import declarations.
This should trigger for requests such as Review Java code for modern Java development; Apply best practices for modern Java development in Java code; Modernize Java code with records pattern matching or switch expressions; Replace legacy idioms with modern Java features; Adopt Java 8+ language features safely.
Part of Plinth Toolkit
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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
Modernize Java code with records pattern matching or switch expressions
Replace legacy idioms with modern Java features
Adopt Java 8+ language features safely
Workflow
Compile project before modernization
Run ./mvnw compile or mvn compile and stop immediately if compilation fails.
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.
Apply modern Java refactorings
Refactor incrementally using appropriate language/library features while preserving behavior and readability.
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).
