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.