Cursor-rules-java 141-java-refactoring-with-modern-features

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

install

source · Clone the upstream repo

git clone https://github.com/jabrena/cursor-rules-java

Claude Code · Install into ~/.claude/skills/

T=$(mktemp -d) && git clone --depth=1 https://github.com/jabrena/cursor-rules-java "$T" && mkdir -p ~/.claude/skills && cp -r "$T/skills/141-java-refactoring-with-modern-features" ~/.claude/skills/jabrena-cursor-rules-java-141-java-refactoring-with-modern-features && rm -rf "$T"

manifest: skills/141-java-refactoring-with-modern-features/SKILL.md

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.