Java Coding Standards Agent Skill

Java coding standards for Spring Boot services: naming, immutability, Optional usage, streams, exceptions, generics, and project layout.

917 tokens

context cost

the whole folder, loaded on every use

files

instructions only

copies elsewhere

how many repositories repackaged it

521

stars on the repo

on the repository, not the skill itself

Install

one command, takes just this skill from the repository

npx skills add https://github.com/vibeeval/vibecosystem --skill java-coding-standards

The instruction itself

14 sections, as written by the author

Java Coding Standards

Standards for readable, maintainable Java (17+) code in Spring Boot services.

Core Principles

Prefer clarity over cleverness
Immutable by default; minimize shared mutable state
Fail fast with meaningful exceptions
Consistent naming and package structure

Naming

// ✅ Classes/Records: PascalCase
public class MarketService {}
public record Money(BigDecimal amount, Currency currency) {}

// ✅ Methods/fields: camelCase
private final MarketRepository marketRepository;
public Market findBySlug(String slug) {}

// ✅ Constants: UPPER_SNAKE_CASE
private static final int MAX_PAGE_SIZE = 100;

Immutability

// ✅ Favor records and final fields
public record MarketDto(Long id, String name, MarketStatus status) {}

public class Market {
  private final Long id;
  private final String name;
  // getters only, no setters
}

Optional Usage

// ✅ Return Optional from find* methods
Optional<Market> market = marketRepository.findBySlug(slug);

// ✅ Map/flatMap instead of get()
return market
    .map(MarketResponse::from)
    .orElseThrow(() -> new EntityNotFoundException("Market not found"));

Streams Best Practices

// ✅ Use streams for transformations, keep pipelines short
List<String> names = markets.stream()
    .map(Market::name)
    .filter(Objects::nonNull)
    .toList();

// ❌ Avoid complex nested streams; prefer loops for clarity

Exceptions

Use unchecked exceptions for domain errors; wrap technical exceptions with context
Create domain-specific exceptions (e.g., MarketNotFoundException)
Avoid broad catch (Exception ex) unless rethrowing/logging centrally

throw new MarketNotFoundException(slug);

Generics and Type Safety

Avoid raw types; declare generic parameters
Prefer bounded generics for reusable utilities

public <T extends Identifiable> Map<Long, T> indexById(Collection<T> items) { ... }

Project Structure (Maven/Gradle)

src/main/java/com/example/app/
  config/
  controller/
  service/
  repository/
  domain/
  dto/
  util/
src/main/resources/
  application.yml
src/test/java/... (mirrors main)

Formatting and Style

Use 2 or 4 spaces consistently (project standard)
One public top-level type per file
Keep methods short and focused; extract helpers
Order members: constants, fields, constructors, public methods, protected, private

Code Smells to Avoid

Long parameter lists → use DTO/builders
Deep nesting → early returns
Magic numbers → named constants
Static mutable state → prefer dependency injection
Silent catch blocks → log and act or rethrow

Logging

private static final Logger log = LoggerFactory.getLogger(MarketService.class);
log.info("fetch_market slug={}", slug);
log.error("failed_fetch_market slug={}", slug, ex);

Null Handling

Accept @Nullable only when unavoidable; otherwise use @NonNull
Use Bean Validation (@NotNull, @NotBlank) on inputs

Testing Expectations

JUnit 5 + AssertJ for fluent assertions
Mockito for mocking; avoid partial mocks where possible
Favor deterministic tests; no hidden sleeps

Remember: Keep code intentional, typed, and observable. Optimize for maintainability over micro-optimizations unless proven necessary.

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How to use it

Copy the folder

Take vibeeval/java-coding-standards from the repository into ~/.claude/skills for personal use, or into .claude/skills inside a project.

Check the name does not clash

The agent identifies a skill by the name field in its header. Two skills with the same name cannot sit side by side — one of them will be ignored.