#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.

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

@@ -127,7 +127,7 @@ public interface EntityLinks extends Plugin<Class<?>> {
 	 * @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 @@ import org.springframework.util.Assert;
 @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 class 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 @@ import org.springframework.web.util.UriTemplate;
  */
 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 @@ public class RepresentationModelProcessorHandlerMethodReturnValueHandler impleme
 			return rootLinksAsHeaders ? HeaderLinksResponseEntity.wrap(newBody) : newBody;
 		}
 
-		HttpEntity<RepresentationModel<?>> entity = null;
+		HttpEntity<RepresentationModel<?>> entity;
 
 		if (originalValue instanceof ResponseEntity) {
 			ResponseEntity<?> source = (ResponseEntity<?>) originalValue;