#1059 - Cleanup the core codebase.

Clean up code containing various patterns:

* Remove redundant `final`, `public`, and `static` declarations in interfaces and enums.
* Replace redundant `? extends Object` generic parameters with `?`.
* Convert collections to arrays using empty array instead of pre-sized one (modern JVM recommendation).
* Initialize collections using constructor call over `addAll`.
* Favor `addAll` over iterating and adding one-by-one.
* Take advantage of `Map.forEach` that was introduced with Java 8.

Author: gregturn

src/main/java/org/springframework/hateoas/AffordanceModel.java

@@ -114,7 +114,7 @@ public boolean pointsToTargetOf(Link link) {
 	 */
 	public interface PayloadMetadata {
 
-		public static PayloadMetadata NONE = NoPayloadMetadata.INSTANCE;
+		PayloadMetadata NONE = NoPayloadMetadata.INSTANCE;
 
 		/**
 		 * Returns all properties contained in a payload.
@@ -135,7 +135,7 @@ default Optional<PropertyMetadata> getPropertyMetadata(String name) {
 	 */
 	public interface InputPayloadMetadata extends PayloadMetadata {
 
-		static InputPayloadMetadata NONE = from(PayloadMetadata.NONE);
+		InputPayloadMetadata NONE = from(PayloadMetadata.NONE);
 
 		static InputPayloadMetadata from(PayloadMetadata metadata) {
 
@@ -298,7 +298,7 @@ public interface Named {
 	 *
 	 * @author Oliver Drotbohm
 	 */
-	private static enum NoPayloadMetadata implements PayloadMetadata {
+	private enum NoPayloadMetadata implements PayloadMetadata {
 
 		INSTANCE;
 

src/main/java/org/springframework/hateoas/Link.java

@@ -202,8 +202,7 @@ public Link andAffordance(Affordance affordance) {
 
 		Assert.notNull(affordance, "Affordance must not be null!");
 
-		List<Affordance> newAffordances = new ArrayList<>();
-		newAffordances.addAll(this.affordances);
+		List<Affordance> newAffordances = new ArrayList<>(this.affordances);
 		newAffordances.add(affordance);
 
 		return withAffordances(newAffordances);
@@ -281,7 +280,7 @@ public Link expand(Object... arguments) {
 	 * @param arguments must not be {@literal null}.
 	 * @return
 	 */
-	public Link expand(Map<String, ? extends Object> arguments) {
+	public Link expand(Map<String, ?> arguments) {
 		return new Link(template.expand(arguments).toString(), getRel());
 	}
 

src/main/java/org/springframework/hateoas/Links.java

@@ -457,7 +457,7 @@ private List<Link> allWithoutRels(Iterable<Link> links) {
 	 *
 	 * @author Oliver Drotbohm
 	 */
-	public static enum MergeMode {
+	public enum MergeMode {
 
 		/**
 		 * Skips to add the same links on merge. Multiple links with the same link relation might appear.
@@ -472,6 +472,6 @@ public static enum MergeMode {
 		/**
 		 * Replaces existing links with the same link relation.
 		 */
-		REPLACE_BY_REL;
+		REPLACE_BY_REL
 	}
 }

src/main/java/org/springframework/hateoas/StringLinkRelation.java

@@ -41,7 +41,7 @@
 class StringLinkRelation implements LinkRelation, Serializable {
 
 	private static final long serialVersionUID = -3904935345545567957L;
-	private static final Map<String, StringLinkRelation> CACHE = new ConcurrentHashMap<String, StringLinkRelation>(256);
+	private static final Map<String, StringLinkRelation> CACHE = new ConcurrentHashMap<>(256);
 
 	@NonNull String relation;
 

src/main/java/org/springframework/hateoas/UriTemplate.java

@@ -267,7 +267,7 @@ public URI expand(Object... parameters) {
 	 * @param parameters must not be {@literal null}.
 	 * @return
 	 */
-	public URI expand(Map<String, ? extends Object> parameters) {
+	public URI expand(Map<String, ?> parameters) {
 
 		if (TemplateVariables.NONE.equals(variables)) {
 			return URI.create(baseUri);
@@ -373,8 +373,7 @@ private static void appendComposite(UriComponentsBuilder builder, String name, O
 
 		} else if (value instanceof Map) {
 
-			((Map<Object, Object>) value).entrySet() //
-					.forEach(it -> builder.queryParam(it.getKey().toString(), it.getValue()));
+			((Map<Object, Object>) value).forEach((key, value1) -> builder.queryParam(key.toString(), value1));
 
 		} else {
 

src/main/java/org/springframework/hateoas/client/Traverson.java

@@ -126,7 +126,7 @@ public static List<HttpMessageConverter<?>> getDefaultMessageConverters(MediaTyp
 		return DEFAULTS.getHttpMessageConverters(Arrays.asList(mediaTypes));
 	}
 
-	private static final RestOperations createDefaultTemplate(List<MediaType> mediaTypes) {
+	private static RestOperations createDefaultTemplate(List<MediaType> mediaTypes) {
 
 		RestTemplate template = new RestTemplate();
 		template.setMessageConverters(DEFAULTS.getHttpMessageConverters(mediaTypes));

src/main/java/org/springframework/hateoas/config/HypermediaConfigurationImportSelector.java

@@ -53,11 +53,6 @@ public String[] selectImports(AnnotationMetadata metadata) {
 		List<MediaTypeConfigurationProvider> configurationProviders = SpringFactoriesLoader.loadFactories(
 				MediaTypeConfigurationProvider.class, HypermediaConfigurationImportSelector.class.getClassLoader());
 
-		// No additional filtering needed.
-		if (types.isEmpty()) {
-			return configurationProviders.toArray(new String[0]);
-		}
-
 		// Filter the ones supporting the given media types
 		return configurationProviders.stream() //
 				.filter(it -> it.supportsAny(types)) //

src/main/java/org/springframework/hateoas/mediatype/MessageResolver.java

@@ -28,7 +28,7 @@
  */
 public interface MessageResolver {
 
-	public static final MessageResolver DEFAULTS_ONLY = DefaultOnlyMessageResolver.INSTANCE;
+	MessageResolver DEFAULTS_ONLY = DefaultOnlyMessageResolver.INSTANCE;
 
 	/**
 	 * Resolve the given {@link MessageSourceResolvable}. Return {@literal null} if no message was found.
@@ -45,7 +45,7 @@ public interface MessageResolver {
 	 * @param messageSource can be {@literal null}.
 	 * @return will never be {@literal null}.
 	 */
-	public static MessageResolver of(@Nullable MessageSource messageSource) {
+	static MessageResolver of(@Nullable MessageSource messageSource) {
 
 		return messageSource == null //
 				? DefaultOnlyMessageResolver.INSTANCE //

src/main/java/org/springframework/hateoas/mediatype/collectionjson/Jackson2CollectionJsonModule.java

@@ -876,7 +876,7 @@ public T deserialize(JsonParser parser, DeserializationContext ctxt) throws IOEx
 
 			return collection.getItems().stream() //
 					.map(CollectionJsonItem::withOwnSelfLink) //
-					.<Object> map(it -> isResource //
+					.map(it -> isResource //
 							? new EntityModel<>(it.toRawData(rootType), it.getLinks()) //
 							: it.toRawData(rootType)) //
 					.collect(Collectors.collectingAndThen(Collectors.toList(), it -> finalizer.apply(it, links)));

src/main/java/org/springframework/hateoas/mediatype/hal/CurieProvider.java

@@ -31,7 +31,7 @@
  */
 public interface CurieProvider {
 
-	public static CurieProvider NONE = new CurieProvider() {
+	CurieProvider NONE = new CurieProvider() {
 
 		@Override
 		public HalLinkRelation getNamespacedRelFrom(Link link) {
@@ -44,7 +44,7 @@ public HalLinkRelation getNamespacedRelFor(LinkRelation rel) {
 		}
 
 		@Override
-		public Collection<? extends Object> getCurieInformation(Links links) {
+		public Collection<?> getCurieInformation(Links links) {
 			throw new UnsupportedOperationException();
 		}
 	};
@@ -75,5 +75,5 @@ public Collection<? extends Object> getCurieInformation(Links links) {
 	 * @param links the {@link Links} that have been added to the response so far.
 	 * @return must not be {@literal null}.
 	 */
-	Collection<? extends Object> getCurieInformation(Links links);
+	Collection<?> getCurieInformation(Links links);
 }

src/main/java/org/springframework/hateoas/mediatype/hal/DefaultCurieProvider.java

@@ -98,7 +98,7 @@ public DefaultCurieProvider(Map<String, UriTemplate> curies, @Nullable String de
 	 * @see org.springframework.hateoas.hal.CurieProvider#getCurieInformation()
 	 */
 	@Override
-	public Collection<? extends Object> getCurieInformation(Links links) {
+	public Collection<?> getCurieInformation(Links links) {
 
 		return curies.entrySet().stream() //
 				.map(it -> new Curie(it.getKey(), getCurieHref(it.getKey(), it.getValue()))) //

src/main/java/org/springframework/hateoas/mediatype/hal/HalTraversonDefaults.java

@@ -80,7 +80,7 @@ public List<LinkDiscoverer> getLinkDiscoverers(Collection<MediaType> mediaTypes)
 	 *
 	 * @return
 	 */
-	private static final HttpMessageConverter<?> getHalConverter(List<MediaType> halFlavours) {
+	private static HttpMessageConverter<?> getHalConverter(List<MediaType> halFlavours) {
 
 		ObjectMapper mapper = new ObjectMapper();
 		mapper.registerModule(new Jackson2HalModule());

src/main/java/org/springframework/hateoas/mediatype/hal/Jackson2HalModule.java

@@ -182,8 +182,7 @@ public void serialize(Links value, JsonGenerator jgen, SerializerProvider provid
 
 			if (!skipCuries && prefixingRequired && curiedLinkPresent) {
 
-				ArrayList<Object> curies = new ArrayList<>();
-				curies.addAll(curieProvider.getCurieInformation(Links.of(links)));
+				ArrayList<Object> curies = new ArrayList<>(curieProvider.getCurieInformation(Links.of(links)));
 
 				sortedLinks.put(HalLinkRelation.CURIES, curies);
 			}
@@ -525,7 +524,7 @@ private void serializeContents(Object value, JsonGenerator jgen, SerializerProvi
 		private JsonSerializer<Object> getOrLookupSerializerFor(Object value, SerializerProvider provider)
 				throws JsonMappingException {
 
-			Class<? extends Object> type = value.getClass();
+			Class<?> type = value.getClass();
 			JsonSerializer<Object> serializer = serializers.get(type);
 
 			if (serializer == null) {

src/main/java/org/springframework/hateoas/mediatype/hal/forms/HalFormsDocument.java

@@ -171,11 +171,11 @@ public HalFormsTemplate getTemplate(String key) {
 	}
 
 	public HalFormsDocument<T> withPageMetadata(@Nullable PageMetadata metadata) {
-		return new HalFormsDocument<T>(attributes, entity, entities, embedded, metadata, links, templates);
+		return new HalFormsDocument<>(attributes, entity, entities, embedded, metadata, links, templates);
 	}
 
 	private HalFormsDocument<T> withEntity(@Nullable T entity) {
-		return new HalFormsDocument<T>(attributes, entity, entities, embedded, pageMetadata, links, templates);
+		return new HalFormsDocument<>(attributes, entity, entities, embedded, pageMetadata, links, templates);
 	}
 
 	/**

src/main/java/org/springframework/hateoas/mediatype/hal/forms/HalFormsTemplateBuilder.java

@@ -206,7 +206,7 @@ public String[] getCodes() {
 
 			codes.add(globalCode);
 
-			return codes.toArray(new String[codes.size()]);
+			return codes.toArray(new String[0]);
 		}
 	}
 }

src/main/java/org/springframework/hateoas/mediatype/uber/Jackson2UberModule.java

@@ -847,7 +847,7 @@ private static CollectionModel<?> extractResources(UberDocument doc, JavaType ro
 				List<LinkRelation> rel = item.getRel();
 
 				if (rel != null) {
-					item.getLinks().forEach(resourceLinks::add);
+					resourceLinks.addAll(item.getLinks());
 				} else {
 
 					// Primitive type

src/main/java/org/springframework/hateoas/server/EntityLinks.java

@@ -127,7 +127,7 @@ default <T> Link linkToItemResource(T entity, Function<T, Object> identifierExtr
 	 * @param extractor the extractor to use to derive an identifier from the given entity.
 	 * @return
 	 */
-	default <T> TypedEntityLinks<T> forType(Function<T, ? extends Object> extractor) {
+	default <T> TypedEntityLinks<T> forType(Function<T, ?> extractor) {
 		return new TypedEntityLinks<>(extractor, this);
 	}
 

src/main/java/org/springframework/hateoas/server/LinkRelationProvider.java

@@ -73,10 +73,10 @@ public interface LinkRelationProvider extends Plugin<LookupContext> {
 	 */
 	@RequiredArgsConstructor(staticName = "of", access = AccessLevel.PRIVATE)
 	@EqualsAndHashCode
-	static class LookupContext {
+	class LookupContext {
 
 		private enum ResourceType {
-			ITEM, COLLECTION;
+			ITEM, COLLECTION
 		}
 
 		private final @NonNull @Getter Class<?> type;

src/main/java/org/springframework/hateoas/server/TypedEntityLinks.java

@@ -35,7 +35,7 @@
 @RequiredArgsConstructor(access = AccessLevel.PACKAGE)
 public class TypedEntityLinks<T> {
 
-	private final @NonNull Function<T, ? extends Object> identifierExtractor;
+	private final @NonNull Function<T, ?> identifierExtractor;
 	private final @NonNull EntityLinks entityLinks;
 
 	/**
@@ -73,7 +73,7 @@ public static class ExtendedTypedEntityLinks<T> extends TypedEntityLinks<T> {
 		private final Class<T> type;
 		private final EntityLinks delegate;
 
-		ExtendedTypedEntityLinks(Function<T, ? extends Object> identifierExtractor, EntityLinks delegate, Class<T> type) {
+		ExtendedTypedEntityLinks(Function<T, ?> identifierExtractor, EntityLinks delegate, Class<T> type) {
 
 			super(identifierExtractor, delegate);
 

src/main/java/org/springframework/hateoas/server/core/UriTemplateFactory.java

@@ -30,7 +30,7 @@
  */
 public class UriTemplateFactory {
 
-	private static final Map<String, UriTemplate> CACHE = new ConcurrentReferenceHashMap<String, UriTemplate>();
+	private static final Map<String, UriTemplate> CACHE = new ConcurrentReferenceHashMap<>();
 
 	/**
 	 * Returns the the {@link UriTemplate} for the given mapping.

src/main/java/org/springframework/hateoas/server/mvc/RepresentationModelProcessorHandlerMethodReturnValueHandler.java

@@ -142,7 +142,7 @@ Object rewrapResult(RepresentationModel<?> newBody, @Nullable Object originalVal
 			return rootLinksAsHeaders ? HeaderLinksResponseEntity.wrap(newBody) : newBody;
 		}
 
-		HttpEntity<RepresentationModel<?>> entity = null;
+		HttpEntity<RepresentationModel<?>> entity;
 
 		if (originalValue instanceof ResponseEntity) {
 			ResponseEntity<?> source = (ResponseEntity<?>) originalValue;

src/test/java/org/springframework/hateoas/mediatype/collectionjson/CollectionJsonWebFluxIntegrationTest.java

@@ -61,12 +61,12 @@ void setUp() {
 	@Test
 	void singleEmployee() {
 
-		this.testClient.get().uri("http://localhost/employees/0")
-				.accept(MediaTypes.COLLECTION_JSON)
-				.exchange()
-				.expectStatus().isOk()
-				.expectHeader().contentType(MediaTypes.COLLECTION_JSON)
-				.expectBody(String.class)
+		this.testClient.get().uri("http://localhost/employees/0") //
+				.accept(MediaTypes.COLLECTION_JSON) //
+				.exchange() //
+				.expectStatus().isOk() //
+				.expectHeader().contentType(MediaTypes.COLLECTION_JSON) //
+				.expectBody(String.class) //
 				.value(jsonPath("$.collection.version", is("1.0")))
 				.value(jsonPath("$.collection.href", is("http://localhost/employees/0")))
 				.value(jsonPath("$.collection.links.*", hasSize(1)))
@@ -96,12 +96,12 @@ void singleEmployee() {
 	@Test
 	void collectionOfEmployees() {
 
-		this.testClient.get().uri("http://localhost/employees")
-				.accept(MediaTypes.COLLECTION_JSON)
-				.exchange()
-				.expectStatus().isOk()
-				.expectHeader().contentType(MediaTypes.COLLECTION_JSON)
-				.expectBody(String.class)
+		this.testClient.get().uri("http://localhost/employees") //
+				.accept(MediaTypes.COLLECTION_JSON) //
+				.exchange() //
+				.expectStatus().isOk() //
+				.expectHeader().contentType(MediaTypes.COLLECTION_JSON) //
+				.expectBody(String.class) //
 
 				.value(jsonPath("$.collection.version", is("1.0")))
 				.value(jsonPath("$.collection.href", is("http://localhost/employees")))
@@ -140,19 +140,19 @@ void createNewEmployee() throws Exception {
 
 		String specBasedJson = read(new ClassPathResource("spec-part7-adjusted.json", getClass()));
 
-		this.testClient.post().uri("http://localhost/employees")
-				.contentType(MediaTypes.COLLECTION_JSON)
-				.syncBody(specBasedJson)
-				.exchange()
-				.expectStatus().isCreated()
+		this.testClient.post().uri("http://localhost/employees") //
+				.contentType(MediaTypes.COLLECTION_JSON) //
+				.syncBody(specBasedJson) //
+				.exchange() //
+				.expectStatus().isCreated() //
 				.expectHeader().valueEquals(HttpHeaders.LOCATION, "http://localhost/employees/2");
 
-		this.testClient.get().uri("http://localhost/employees/2")
-				.accept(MediaTypes.COLLECTION_JSON)
-				.exchange()
-				.expectStatus().isOk()
-				.expectHeader().contentType(MediaTypes.COLLECTION_JSON)
-				.expectBody(String.class)
+		this.testClient.get().uri("http://localhost/employees/2") //
+				.accept(MediaTypes.COLLECTION_JSON) //
+				.exchange() //
+				.expectStatus().isOk() //
+				.expectHeader().contentType(MediaTypes.COLLECTION_JSON) //
+				.expectBody(String.class) //
 
 				.value(jsonPath("$.collection.version", is("1.0")))
 				.value(jsonPath("$.collection.href", is("http://localhost/employees/2")))
@@ -190,11 +190,11 @@ WebFluxEmployeeController employeeController() {
 
 		@Bean
 		WebTestClient webTestClient(WebClientConfigurer webClientConfigurer, ApplicationContext ctx) {
-			
-			return WebTestClient.bindToApplicationContext(ctx).build()
-				.mutate()
-				.exchangeStrategies(webClientConfigurer.hypermediaExchangeStrategies())
-				.build();
+
+			return WebTestClient.bindToApplicationContext(ctx).build() //
+					.mutate() //
+					.exchangeStrategies(webClientConfigurer.hypermediaExchangeStrategies()) //
+					.build();
 		}
 	}
 }

src/test/java/org/springframework/hateoas/mediatype/hal/forms/HalFormsWebFluxIntegrationTest.java

@@ -122,8 +122,10 @@ void createNewEmployee() throws Exception {
 		String specBasedJson = MappingUtils.read(new ClassPathResource("new-employee.json", getClass()));
 
 		this.testClient.post().uri("http://localhost/employees").contentType(MediaTypes.HAL_FORMS_JSON)
-				.syncBody(specBasedJson).exchange().expectStatus().isCreated().expectHeader()
-				.valueEquals(HttpHeaders.LOCATION, "http://localhost/employees/2");
+				.syncBody(specBasedJson) //
+				.exchange() //
+				.expectStatus().isCreated() //
+				.expectHeader().valueEquals(HttpHeaders.LOCATION, "http://localhost/employees/2");
 	}
 
 	@Configuration