Java Coding Standards

// PASS: Classes/Records: PascalCasepublic class MarketService {}public record Money(BigDecimal amount, Currency currency) {}
// PASS: Methods/fields: camelCaseprivate final MarketRepository marketRepository;public Market findBySlug(String slug) {}
// PASS: Constants: UPPER_SNAKE_CASEprivate static final int MAX_PAGE_SIZE = 100;
// PASS: [QUARKUS] JAX-RS resources named as *Resource, not *Controllerpublic class MarketResource {}
// PASS: [SPRING] REST controllers named as *Controllerpublic class MarketController {}

// PASS: Favor records and final fieldspublic record MarketDto(Long id, String name, MarketStatus status) {}
public class Market {  private final Long id;  private final String name;  // getters only, no setters}
// PASS: [QUARKUS] Panache active-record entities use public fields (Quarkus convention)@Entitypublic class Market extends PanacheEntity {  public String name;  public MarketStatus status;  // Panache generates accessors at build time; public fields are idiomatic here}
// PASS: [QUARKUS] Panache MongoDB entities@MongoEntity(collection = "markets")public class Market extends PanacheMongoEntity {  public String name;  public MarketStatus status;}

// PASS: Return Optional from find* methods// [SPRING]Optional<Market> market = marketRepository.findBySlug(slug);
// [QUARKUS] PanacheOptional<Market> market = Market.find("slug", slug).firstResultOptional();
// PASS: Map/flatMap instead of get()return market    .map(MarketResponse::from)    .orElseThrow(() -> new EntityNotFoundException("Market not found"));

// PASS: Use streams for transformations, keep pipelines shortList<String> names = markets.stream()    .map(Market::name)    .filter(Objects::nonNull)    .toList();
// FAIL: Avoid complex nested streams; prefer loops for clarity

// PASS: [SPRING] Constructor injection (preferred over @Autowired on fields)@Servicepublic class MarketService {  private final MarketRepository marketRepository;
  public MarketService(MarketRepository marketRepository) {    this.marketRepository = marketRepository;  }}
// PASS: [QUARKUS] Constructor injection@ApplicationScopedpublic class MarketService {  private final MarketRepository marketRepository;
  @Inject  public MarketService(MarketRepository marketRepository) {    this.marketRepository = marketRepository;  }}
// PASS: [QUARKUS] Package-private field injection (acceptable in Quarkus — avoids proxy issues)@ApplicationScopedpublic class MarketService {  @Inject  MarketRepository marketRepository;}
// FAIL: [SPRING] Field injection with @Autowired@Autowiredprivate MarketRepository marketRepository; // use constructor injection
// FAIL: [QUARKUS] @Singleton when interception or lazy init is needed@Singleton // non-proxyable — use @ApplicationScoped insteadpublic class MarketService {}

// PASS: Return Uni/Multi from reactive endpoints@GET@Path("/{slug}")public Uni<Market> findBySlug(@PathParam("slug") String slug) {  return Market.find("slug", slug)      .<Market>firstResult()      .onItem().ifNull().failWith(() -> new MarketNotFoundException(slug));}
// PASS: Non-blocking pipeline compositionpublic Uni<OrderConfirmation> placeOrder(OrderRequest req) {  return validateOrder(req)      .chain(valid -> persistOrder(valid))      .chain(order -> notifyFulfillment(order));}
// FAIL: Blocking call inside a Uni/Multi pipelinepublic Uni<Market> find(String slug) {  Market m = Market.find("slug", slug).firstResult(); // BLOCKING — breaks event loop  return Uni.createFrom().item(m);}
// FAIL: Subscribing more than once to a shared UniUni<Market> shared = fetchMarket(slug);shared.subscribe().with(m -> log(m));shared.subscribe().with(m -> cache(m)); // double subscribe — use Uni.memoize()

throw new MarketNotFoundException(slug);

// [SPRING]@RestControllerAdvicepublic class GlobalExceptionHandler {  @ExceptionHandler(MarketNotFoundException.class)  public ResponseEntity<ErrorResponse> handle(MarketNotFoundException ex) {    return ResponseEntity.status(404).body(ErrorResponse.from(ex));  }}
// [QUARKUS] Option A: ExceptionMapper@Providerpublic class MarketNotFoundMapper implements ExceptionMapper<MarketNotFoundException> {  @Override  public Response toResponse(MarketNotFoundException ex) {    return Response.status(404).entity(ErrorResponse.from(ex)).build();  }}
// [QUARKUS] Option B: @ServerExceptionMapper (RESTEasy Reactive)@ServerExceptionMapperpublic RestResponse<ErrorResponse> handle(MarketNotFoundException ex) {  return RestResponse.status(Status.NOT_FOUND, ErrorResponse.from(ex));}

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

// [SPRING] SLF4Jprivate static final Logger log = LoggerFactory.getLogger(MarketService.class);log.info("fetch_market slug={}", slug);log.error("failed_fetch_market slug={}", slug, ex);
// [QUARKUS] JBoss Logging (default, zero-cost at build time)private static final Logger log = Logger.getLogger(MarketService.class);log.infof("fetch_market slug=%s", slug);log.errorf(ex, "failed_fetch_market slug=%s", slug);
// [QUARKUS] Alternative: simplified logging with @Inject@InjectLogger log; // CDI-injected, scoped to declaring class

// [SPRING] @ConfigurationProperties@ConfigurationProperties(prefix = "market")public record MarketProperties(int maxPageSize, Duration cacheTtl) {}
// [QUARKUS] @ConfigMapping (type-safe, build-time validated)@ConfigMapping(prefix = "market")public interface MarketConfig {  int maxPageSize();  Duration cacheTtl();}
// [QUARKUS] Simple values with @ConfigProperty@ConfigProperty(name = "market.max-page-size", defaultValue = "100")int maxPageSize;

// [SPRING] Controller test@WebMvcTest(MarketController.class)class MarketControllerTest {  @Autowired MockMvc mockMvc;  @MockBean MarketService marketService;}
// [QUARKUS] Integration test@QuarkusTestclass MarketResourceTest {  @InjectMock  MarketService marketService;
  @Test  void should_return_404_when_market_not_found() {    given().when().get("/markets/unknown").then().statusCode(404);  }}
// [QUARKUS] Unit test (no CDI, no @QuarkusTest)@ExtendWith(MockitoExtension.class)class MarketServiceTest {  @Mock MarketRepository marketRepository;  @InjectMocks MarketService marketService;}