141-java-refactoring-with-modern-features

name	141-java-refactoring-with-modern-features
description	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. Part of the skills-for-java project
license	Apache-2.0
metadata	{"author":"Juan Antonio Breña Moral","version":"0.13.0-SNAPSHOT"}

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

When to use this skill

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

Reference

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