Modern Java Development Guidelines (Java 8+)

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

Core areas: 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()), CompletableFuture for composable async programming, text blocks for multi-line strings, Java 25 Flexible Constructor Bodies (JEP 513), and Java 25 Module Import Declarations (JEP 511).

Prerequisites: Run ./mvnw compile or mvn compile before applying any changes. If compilation fails, stop immediately — do not proceed until the project compiles successfully.

Multi-step scope: Step 1 validates compilation. Step 2 categorizes refactoring opportunities by impact (CRITICAL, MAINTAINABILITY, PERFORMANCE, READABILITY). Step 3 applies lambda/method-reference conversions. Step 4 replaces imperative loops with Stream API pipelines. Step 5 introduces Optional for null-safe method returns. Step 6 migrates legacy date/time to java.time. Step 7 adopts collection factory methods and async CompletableFuture patterns. Step 8 applies text blocks, var, and Java 25 features where applicable. Step 9 runs ./mvnw clean verify to confirm all tests pass after changes.

Before applying changes: Read the reference for detailed good/bad examples, constraints, and safeguards for each modern Java feature.

Reference

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