Use EnumMap whenever possible

Replace regular Map instances with EnumMap to reduce memory consumption.

Closes gh-11760

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/endpoint/annotation/DiscoveredOperationsFactory.java

@@ -20,7 +20,7 @@ import java.lang.annotation.Annotation;
 import java.lang.reflect.Method;
 import java.util.Collection;
 import java.util.Collections;
-import java.util.LinkedHashMap;
+import java.util.EnumMap;
 import java.util.Map;
 import java.util.Objects;
 
@@ -50,7 +50,8 @@ abstract class DiscoveredOperationsFactory<O extends Operation> {
 	private static final Map<OperationType, Class<? extends Annotation>> OPERATION_TYPES;
 
 	static {
-		Map<OperationType, Class<? extends Annotation>> operationTypes = new LinkedHashMap<>();
+		Map<OperationType, Class<? extends Annotation>> operationTypes = new EnumMap<>(
+				OperationType.class);
 		operationTypes.put(OperationType.READ, ReadOperation.class);
 		operationTypes.put(OperationType.WRITE, WriteOperation.class);
 		operationTypes.put(OperationType.DELETE, DeleteOperation.class);

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/cache/CacheConfigurations.java

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,7 +17,7 @@
 package org.springframework.boot.autoconfigure.cache;
 
 import java.util.Collections;
-import java.util.HashMap;
+import java.util.EnumMap;
 import java.util.Map;
 
 import org.springframework.util.Assert;
@@ -33,7 +33,7 @@ final class CacheConfigurations {
 	private static final Map<CacheType, Class<?>> MAPPINGS;
 
 	static {
-		Map<CacheType, Class<?>> mappings = new HashMap<>();
+		Map<CacheType, Class<?>> mappings = new EnumMap<>(CacheType.class);
 		mappings.put(CacheType.GENERIC, GenericCacheConfiguration.class);
 		mappings.put(CacheType.EHCACHE, EhCacheCacheConfiguration.class);
 		mappings.put(CacheType.HAZELCAST, HazelcastCacheConfiguration.class);

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jackson/JacksonProperties.java

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,7 +16,7 @@
 
 package org.springframework.boot.autoconfigure.jackson;
 
-import java.util.HashMap;
+import java.util.EnumMap;
 import java.util.Locale;
 import java.util.Map;
 import java.util.TimeZone;
@@ -63,27 +63,31 @@ public class JacksonProperties {
 	/**
 	 * Jackson on/off features that affect the way Java objects are serialized.
 	 */
-	private Map<SerializationFeature, Boolean> serialization = new HashMap<>();
+	private Map<SerializationFeature, Boolean> serialization = new EnumMap<>(
+			SerializationFeature.class);
 
 	/**
 	 * Jackson on/off features that affect the way Java objects are deserialized.
 	 */
-	private Map<DeserializationFeature, Boolean> deserialization = new HashMap<>();
+	private Map<DeserializationFeature, Boolean> deserialization = new EnumMap<>(
+			DeserializationFeature.class);
 
 	/**
 	 * Jackson general purpose on/off features.
 	 */
-	private Map<MapperFeature, Boolean> mapper = new HashMap<>();
+	private Map<MapperFeature, Boolean> mapper = new EnumMap<>(MapperFeature.class);
 
 	/**
 	 * Jackson on/off features for parsers.
 	 */
-	private Map<JsonParser.Feature, Boolean> parser = new HashMap<>();
+	private Map<JsonParser.Feature, Boolean> parser = new EnumMap<>(
+			JsonParser.Feature.class);
 
 	/**
 	 * Jackson on/off features for generators.
 	 */
-	private Map<JsonGenerator.Feature, Boolean> generator = new HashMap<>();
+	private Map<JsonGenerator.Feature, Boolean> generator = new EnumMap<>(
+			JsonGenerator.Feature.class);
 
 	/**
 	 * Controls the inclusion of properties during serialization. Configured with one of

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jooq/SqlDialectLookup.java

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,7 +17,7 @@
 package org.springframework.boot.autoconfigure.jooq;
 
 import java.util.Collections;
-import java.util.HashMap;
+import java.util.EnumMap;
 import java.util.Map;
 
 import javax.sql.DataSource;
@@ -42,7 +42,7 @@ final class SqlDialectLookup {
 	private static final Map<DatabaseDriver, SQLDialect> LOOKUP;
 
 	static {
-		Map<DatabaseDriver, SQLDialect> map = new HashMap<>();
+		Map<DatabaseDriver, SQLDialect> map = new EnumMap<>(DatabaseDriver.class);
 		map.put(DatabaseDriver.DERBY, SQLDialect.DERBY);
 		map.put(DatabaseDriver.H2, SQLDialect.H2);
 		map.put(DatabaseDriver.HSQLDB, SQLDialect.HSQLDB);

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/orm/jpa/DatabaseLookup.java

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,7 +17,7 @@
 package org.springframework.boot.autoconfigure.orm.jpa;
 
 import java.util.Collections;
-import java.util.HashMap;
+import java.util.EnumMap;
 import java.util.Map;
 
 import javax.sql.DataSource;
@@ -43,7 +43,7 @@ final class DatabaseLookup {
 	private static final Map<DatabaseDriver, Database> LOOKUP;
 
 	static {
-		Map<DatabaseDriver, Database> map = new HashMap<>();
+		Map<DatabaseDriver, Database> map = new EnumMap<>(DatabaseDriver.class);
 		map.put(DatabaseDriver.DERBY, Database.DERBY);
 		map.put(DatabaseDriver.H2, Database.H2);
 		map.put(DatabaseDriver.HSQLDB, Database.HSQL);

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/session/SessionStoreMappings.java

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,7 +17,7 @@
 package org.springframework.boot.autoconfigure.session;
 
 import java.util.Collections;
-import java.util.HashMap;
+import java.util.EnumMap;
 import java.util.Map;
 
 import org.springframework.boot.WebApplicationType;
@@ -34,7 +34,8 @@ final class SessionStoreMappings {
 	private static final Map<StoreType, Map<WebApplicationType, Class<?>>> MAPPINGS;
 
 	static {
-		Map<StoreType, Map<WebApplicationType, Class<?>>> mappings = new HashMap<>();
+		Map<StoreType, Map<WebApplicationType, Class<?>>> mappings = new EnumMap<>(
+				StoreType.class);
 		mappings.put(StoreType.REDIS, createMapping(RedisSessionConfiguration.class,
 				RedisReactiveSessionConfiguration.class));
 		mappings.put(StoreType.MONGODB, createMapping(MongoSessionConfiguration.class,
@@ -54,7 +55,8 @@ final class SessionStoreMappings {
 
 	static Map<WebApplicationType, Class<?>> createMapping(Class<?> servletConfiguration,
 			Class<?> reactiveConfiguration) {
-		Map<WebApplicationType, Class<?>> mapping = new HashMap<>();
+		Map<WebApplicationType, Class<?>> mapping = new EnumMap<>(
+				WebApplicationType.class);
 		mapping.put(WebApplicationType.SERVLET, servletConfiguration);
 		if (reactiveConfiguration != null) {
 			mapping.put(WebApplicationType.REACTIVE, reactiveConfiguration);

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/reactive/error/DefaultErrorWebExceptionHandler.java

@@ -17,7 +17,7 @@
 package org.springframework.boot.autoconfigure.web.reactive.error;
 
 import java.util.Collections;
-import java.util.HashMap;
+import java.util.EnumMap;
 import java.util.List;
 import java.util.Map;
 
@@ -79,7 +79,7 @@ public class DefaultErrorWebExceptionHandler extends AbstractErrorWebExceptionHa
 			.getLog(DefaultErrorWebExceptionHandler.class);
 
 	static {
-		Map<HttpStatus.Series, String> views = new HashMap<>();
+		Map<HttpStatus.Series, String> views = new EnumMap<>(HttpStatus.Series.class);
 		views.put(HttpStatus.Series.CLIENT_ERROR, "4xx");
 		views.put(HttpStatus.Series.SERVER_ERROR, "5xx");
 		SERIES_VIEWS = Collections.unmodifiableMap(views);

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/servlet/error/DefaultErrorViewResolver.java

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,7 +17,7 @@
 package org.springframework.boot.autoconfigure.web.servlet.error;
 
 import java.util.Collections;
-import java.util.HashMap;
+import java.util.EnumMap;
 import java.util.Map;
 
 import javax.servlet.http.HttpServletRequest;
@@ -60,7 +60,7 @@ public class DefaultErrorViewResolver implements ErrorViewResolver, Ordered {
 	private static final Map<Series, String> SERIES_VIEWS;
 
 	static {
-		Map<Series, String> views = new HashMap<>();
+		Map<Series, String> views = new EnumMap<>(Series.class);
 		views.put(Series.CLIENT_ERROR, "4xx");
 		views.put(Series.SERVER_ERROR, "5xx");
 		SERIES_VIEWS = Collections.unmodifiableMap(views);

spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/remote/client/ClassPathChangeUploader.java

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,7 +25,7 @@ import java.net.URI;
 import java.net.URISyntaxException;
 import java.net.URL;
 import java.util.Collections;
-import java.util.HashMap;
+import java.util.EnumMap;
 import java.util.Map;
 
 import org.apache.commons.logging.Log;
@@ -61,7 +61,8 @@ public class ClassPathChangeUploader
 	private static final Map<ChangedFile.Type, ClassLoaderFile.Kind> TYPE_MAPPINGS;
 
 	static {
-		Map<ChangedFile.Type, ClassLoaderFile.Kind> map = new HashMap<>();
+		Map<ChangedFile.Type, ClassLoaderFile.Kind> map = new EnumMap<>(
+				ChangedFile.Type.class);
 		map.put(ChangedFile.Type.ADD, ClassLoaderFile.Kind.ADDED);
 		map.put(ChangedFile.Type.DELETE, ClassLoaderFile.Kind.DELETED);
 		map.put(ChangedFile.Type.MODIFY, ClassLoaderFile.Kind.MODIFIED);

spring-boot-project/spring-boot-tools/spring-boot-configuration-processor/src/main/java/org/springframework/boot/configurationprocessor/TypeUtils.java

@@ -18,6 +18,7 @@ package org.springframework.boot.configurationprocessor;
 
 import java.util.Collection;
 import java.util.Collections;
+import java.util.EnumMap;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.stream.Collectors;
@@ -45,7 +46,7 @@ class TypeUtils {
 	private static final Map<TypeKind, Class<?>> PRIMITIVE_WRAPPERS;
 
 	static {
-		Map<TypeKind, Class<?>> wrappers = new HashMap<>();
+		Map<TypeKind, Class<?>> wrappers = new EnumMap<>(TypeKind.class);
 		wrappers.put(TypeKind.BOOLEAN, Boolean.class);
 		wrappers.put(TypeKind.BYTE, Byte.class);
 		wrappers.put(TypeKind.CHAR, Character.class);

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/ansi/AnsiColors.java

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,7 +19,7 @@ package org.springframework.boot.ansi;
 import java.awt.Color;
 import java.awt.color.ColorSpace;
 import java.util.Collections;
-import java.util.LinkedHashMap;
+import java.util.EnumMap;
 import java.util.Map;
 import java.util.Map.Entry;
 
@@ -39,7 +39,7 @@ public final class AnsiColors {
 	private static final Map<AnsiColor, LabColor> ANSI_COLOR_MAP;
 
 	static {
-		Map<AnsiColor, LabColor> colorMap = new LinkedHashMap<>();
+		Map<AnsiColor, LabColor> colorMap = new EnumMap<>(AnsiColor.class);
 		colorMap.put(AnsiColor.BLACK, new LabColor(0x000000));
 		colorMap.put(AnsiColor.RED, new LabColor(0xAA0000));
 		colorMap.put(AnsiColor.GREEN, new LabColor(0x00AA00));

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/logging/AbstractLoggingSystem.java

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,6 +17,7 @@
 package org.springframework.boot.logging;
 
 import java.util.Comparator;
+import java.util.EnumMap;
 import java.util.HashMap;
 import java.util.LinkedHashSet;
 import java.util.Map;
@@ -194,7 +195,7 @@ public abstract class AbstractLoggingSystem extends LoggingSystem {
 		private final Map<T, LogLevel> nativeToSystem;
 
 		public LogLevels() {
-			this.systemToNative = new HashMap<>();
+			this.systemToNative = new EnumMap<>(LogLevel.class);
 			this.nativeToSystem = new HashMap<>();
 		}