Initialize pre-filled HashMaps with large enough capacity

Empty Maps are preferably initialized without capacity (not initializing them at all or lazily initializing with default capacity when needed).

Issue: SPR-17105

spring-beans/src/main/java/org/springframework/beans/factory/config/ConstructorArgumentValues.java

@@ -43,7 +43,7 @@ import org.springframework.util.ObjectUtils;
  */
 public class ConstructorArgumentValues {
 
-	private final Map<Integer, ValueHolder> indexedArgumentValues = new LinkedHashMap<>(0);
+	private final Map<Integer, ValueHolder> indexedArgumentValues = new LinkedHashMap<>();
 
 	private final List<ValueHolder> genericArgumentValues = new ArrayList<>();
 

spring-beans/src/main/java/org/springframework/beans/factory/support/AbstractBeanDefinition.java

@@ -158,7 +158,7 @@ public abstract class AbstractBeanDefinition extends BeanMetadataAttributeAccess
 
 	private boolean primary = false;
 
-	private final Map<String, AutowireCandidateQualifier> qualifiers = new LinkedHashMap<>(0);
+	private final Map<String, AutowireCandidateQualifier> qualifiers = new LinkedHashMap<>();
 
 	@Nullable
 	private Supplier<?> instanceSupplier;

spring-context/src/main/java/org/springframework/cache/interceptor/CacheAspectSupport.java

@@ -410,7 +410,7 @@ public abstract class CacheAspectSupport extends AbstractCacheInvoker
 		Object cacheValue;
 		Object returnValue;
 
-		if (cacheHit != null && cachePutRequests.isEmpty() && !hasCachePut(contexts)) {
+		if (cacheHit != null && !hasCachePut(contexts)) {
 			// If there are no put requests, just use the cache hit
 			cacheValue = cacheHit.get();
 			returnValue = wrapCacheValue(method, cacheValue);

spring-context/src/main/java/org/springframework/scheduling/concurrent/ConcurrentTaskExecutor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -230,17 +230,21 @@ public class ConcurrentTaskExecutor implements AsyncListenableTaskExecutor, Sche
 	protected static class ManagedTaskBuilder {
 
 		public static Runnable buildManagedTask(Runnable task, String identityName) {
-			Map<String, String> properties = new HashMap<>(2);
+			Map<String, String> properties;
 			if (task instanceof SchedulingAwareRunnable) {
+				properties = new HashMap<>(4);
 				properties.put(ManagedTask.LONGRUNNING_HINT,
 						Boolean.toString(((SchedulingAwareRunnable) task).isLongLived()));
 			}
+			else {
+				properties = new HashMap<>(2);
+			}
 			properties.put(ManagedTask.IDENTITY_NAME, identityName);
 			return ManagedExecutors.managedTask(task, properties, null);
 		}
 
 		public static <T> Callable<T> buildManagedTask(Callable<T> task, String identityName) {
-			Map<String, String> properties = new HashMap<>(1);
+			Map<String, String> properties = new HashMap<>(2);
 			properties.put(ManagedTask.IDENTITY_NAME, identityName);
 			return ManagedExecutors.managedTask(task, properties, null);
 		}

spring-context/src/main/java/org/springframework/validation/AbstractBindingResult.java

@@ -52,9 +52,9 @@ public abstract class AbstractBindingResult extends AbstractErrors implements Bi
 
 	private final List<ObjectError> errors = new LinkedList<>();
 
-	private final Map<String, Class<?>> fieldTypes = new HashMap<>(0);
+	private final Map<String, Class<?>> fieldTypes = new HashMap<>();
 
-	private final Map<String, Object> fieldValues = new HashMap<>(0);
+	private final Map<String, Object> fieldValues = new HashMap<>();
 
 	private final Set<String> suppressedFields = new HashSet<>();
 

spring-core/src/main/java/org/springframework/core/AttributeAccessorSupport.java

@@ -38,7 +38,7 @@ import org.springframework.util.StringUtils;
 public abstract class AttributeAccessorSupport implements AttributeAccessor, Serializable {
 
 	/** Map with String keys and Object values. */
-	private final Map<String, Object> attributes = new LinkedHashMap<>(0);
+	private final Map<String, Object> attributes = new LinkedHashMap<>();
 
 
 	@Override

spring-jdbc/src/main/java/org/springframework/jdbc/core/simple/AbstractJdbcInsert.java

@@ -465,7 +465,7 @@ public abstract class AbstractJdbcInsert {
 			if (keyQuery.toUpperCase().startsWith("RETURNING")) {
 				Long key = getJdbcTemplate().queryForObject(
 						getInsertString() + " " + keyQuery, values.toArray(), Long.class);
-				Map<String, Object> keys = new HashMap<>(1);
+				Map<String, Object> keys = new HashMap<>(2);
 				keys.put(getGeneratedKeyNames()[0], key);
 				keyHolder.getKeyList().add(keys);
 			}
@@ -484,7 +484,7 @@ public abstract class AbstractJdbcInsert {
 					//Get the key
 					Statement keyStmt = null;
 					ResultSet rs = null;
-					Map<String, Object> keys = new HashMap<>(1);
+					Map<String, Object> keys = new HashMap<>(2);
 					try {
 						keyStmt = con.createStatement();
 						rs = keyStmt.executeQuery(keyQuery);

spring-messaging/src/main/java/org/springframework/messaging/MessageHeaders.java

@@ -164,7 +164,7 @@ public class MessageHeaders implements Map<String, Object>, Serializable {
 	 * @param keysToIgnore the keys of the entries to ignore
 	 */
 	private MessageHeaders(MessageHeaders original, Set<String> keysToIgnore) {
-		this.headers = new HashMap<>(original.headers.size() - keysToIgnore.size());
+		this.headers = new HashMap<>(original.headers.size());
 		original.headers.forEach((key, value) -> {
 			if (!keysToIgnore.contains(key)) {
 				this.headers.put(key, value);

spring-messaging/src/main/java/org/springframework/messaging/simp/broker/AbstractSubscriptionRegistry.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -38,7 +38,7 @@ import org.springframework.util.MultiValueMap;
 public abstract class AbstractSubscriptionRegistry implements SubscriptionRegistry {
 
 	private static final MultiValueMap<String, String> EMPTY_MAP =
-			CollectionUtils.unmodifiableMultiValueMap(new LinkedMultiValueMap<>(0));
+			CollectionUtils.unmodifiableMultiValueMap(new LinkedMultiValueMap<>());
 
 	protected final Log logger = SimpLogging.forLogName(getClass());
 

spring-messaging/src/main/java/org/springframework/messaging/simp/config/AbstractMessageBrokerConfiguration.java

@@ -317,7 +317,7 @@ public abstract class AbstractMessageBrokerConfiguration implements ApplicationC
 		if (handler == null) {
 			return null;
 		}
-		Map<String, MessageHandler> subscriptions = new HashMap<>(1);
+		Map<String, MessageHandler> subscriptions = new HashMap<>(4);
 		String destination = getBrokerRegistry().getUserDestinationBroadcast();
 		if (destination != null) {
 			subscriptions.put(destination, userDestinationMessageHandler());

spring-messaging/src/main/java/org/springframework/messaging/simp/user/MultiServerUserRegistry.java

@@ -545,7 +545,7 @@ public class MultiServerUserRegistry implements SimpUserRegistry, SmartApplicati
 	private class SessionLookup {
 
 		public Map<String, SimpSession> findSessions(String userName) {
-			Map<String, SimpSession> map = new HashMap<>(1);
+			Map<String, SimpSession> map = new HashMap<>(4);
 			SimpUser user = localRegistry.getUser(userName);
 			if (user != null) {
 				for (SimpSession session : user.getSessions()) {

spring-web/src/main/java/org/springframework/http/HttpHeaders.java

@@ -78,7 +78,7 @@ public class HttpHeaders implements MultiValueMap<String, String>, Serializable
 	/**
 	 * The empty {@code HttpHeaders} instance (immutable).
 	 */
-	public static final HttpHeaders EMPTY = new HttpHeaders(new LinkedHashMap<>(0), true);
+	public static final HttpHeaders EMPTY = new HttpHeaders(new LinkedHashMap<>(), true);
 	/**
 	 * The HTTP {@code Accept} header field name.
 	 * @see <a href="http://tools.ietf.org/html/rfc7231#section-5.3.2">Section 5.3.2 of RFC 7231</a>

spring-web/src/main/java/org/springframework/http/HttpMethod.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -35,7 +35,7 @@ public enum HttpMethod {
 	GET, HEAD, POST, PUT, PATCH, DELETE, OPTIONS, TRACE;
 
 
-	private static final Map<String, HttpMethod> mappings = new HashMap<>(8);
+	private static final Map<String, HttpMethod> mappings = new HashMap<>(16);
 
 	static {
 		for (HttpMethod httpMethod : values()) {

spring-web/src/main/java/org/springframework/http/server/DefaultPathContainer.java

@@ -38,7 +38,7 @@ import org.springframework.util.StringUtils;
  */
 final class DefaultPathContainer implements PathContainer {
 
-	private static final MultiValueMap<String, String> EMPTY_MAP = new LinkedMultiValueMap<>(0);
+	private static final MultiValueMap<String, String> EMPTY_MAP = new LinkedMultiValueMap<>();
 
 	private static final PathContainer EMPTY_PATH = new DefaultPathContainer("", Collections.emptyList());
 

spring-web/src/main/java/org/springframework/web/util/HierarchicalUriComponents.java

@@ -55,54 +55,46 @@ final class HierarchicalUriComponents extends UriComponents {
 
 	private static final String PATH_DELIMITER_STRING = "/";
 
+	private static final MultiValueMap<String, String> EMPTY_QUERY_PARAMS =
+			CollectionUtils.unmodifiableMultiValueMap(new LinkedMultiValueMap<>());
+
 
 	/**
 	 * Represents an empty path.
 	 */
 	static final PathComponent NULL_PATH_COMPONENT = new PathComponent() {
-
 		@Override
 		public String getPath() {
 			return "";
 		}
-
 		@Override
 		public List<String> getPathSegments() {
 			return Collections.emptyList();
 		}
-
 		@Override
 		public PathComponent encode(BiFunction<String, Type, String> encoder) {
 			return this;
 		}
-
 		@Override
 		public void verify() {
 		}
-
 		@Override
 		public PathComponent expand(UriTemplateVariables uriVariables, @Nullable UnaryOperator<String> encoder) {
 			return this;
 		}
-
 		@Override
 		public void copyToUriComponentsBuilder(UriComponentsBuilder builder) {
 		}
-
 		@Override
 		public boolean equals(Object other) {
 			return (this == other);
 		}
-
 		@Override
 		public int hashCode() {
 			return getClass().hashCode();
 		}
 	};
 
-	private static final MultiValueMap<String, String> EMPTY_QUERY_PARAMS =
-			CollectionUtils.unmodifiableMultiValueMap(new LinkedMultiValueMap<>(0));
-
 
 	@Nullable
 	private final String userInfo;

spring-web/src/main/java/org/springframework/web/util/HtmlCharacterEntityReferences.java

@@ -55,7 +55,7 @@ class HtmlCharacterEntityReferences {
 
 	private final String[] characterToEntityReferenceMap = new String[3000];
 
-	private final Map<String, Character> entityReferenceToCharacterMap = new HashMap<>(252);
+	private final Map<String, Character> entityReferenceToCharacterMap = new HashMap<>(512);
 
 
 	/**

spring-web/src/main/java/org/springframework/web/util/OpaqueUriComponents.java

@@ -38,7 +38,7 @@ import org.springframework.util.ObjectUtils;
 @SuppressWarnings("serial")
 final class OpaqueUriComponents extends UriComponents {
 
-	private static final MultiValueMap<String, String> QUERY_PARAMS_NONE = new LinkedMultiValueMap<>(0);
+	private static final MultiValueMap<String, String> QUERY_PARAMS_NONE = new LinkedMultiValueMap<>();
 
 	@Nullable
 	private final String ssp;

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultWebClient.java

@@ -349,7 +349,7 @@ class DefaultWebClient implements WebClient {
 
 		private MultiValueMap<String, String> initCookies() {
 			if (CollectionUtils.isEmpty(this.cookies)) {
-				return (defaultCookies != null ? defaultCookies : new LinkedMultiValueMap<>(0));
+				return (defaultCookies != null ? defaultCookies : new LinkedMultiValueMap<>());
 			}
 			else if (CollectionUtils.isEmpty(defaultCookies)) {
 				return this.cookies;

spring-webflux/src/main/java/org/springframework/web/reactive/socket/adapter/NettyWebSocketSessionSupport.java

@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.web.reactive.socket.adapter;
 
 import java.util.HashMap;
@@ -49,14 +50,14 @@ public abstract class NettyWebSocketSessionSupport<T> extends AbstractWebSocketS
 	protected static final int DEFAULT_FRAME_MAX_SIZE = 64 * 1024;
 
 
-	private static final Map<Class<?>, WebSocketMessage.Type> MESSAGE_TYPES;
+	private static final Map<Class<?>, WebSocketMessage.Type> messageTypes;
 
 	static {
-		MESSAGE_TYPES = new HashMap<>(4);
-		MESSAGE_TYPES.put(TextWebSocketFrame.class, WebSocketMessage.Type.TEXT);
-		MESSAGE_TYPES.put(BinaryWebSocketFrame.class, WebSocketMessage.Type.BINARY);
-		MESSAGE_TYPES.put(PingWebSocketFrame.class, WebSocketMessage.Type.PING);
-		MESSAGE_TYPES.put(PongWebSocketFrame.class, WebSocketMessage.Type.PONG);
+		messageTypes = new HashMap<>(8);
+		messageTypes.put(TextWebSocketFrame.class, WebSocketMessage.Type.TEXT);
+		messageTypes.put(BinaryWebSocketFrame.class, WebSocketMessage.Type.BINARY);
+		messageTypes.put(PingWebSocketFrame.class, WebSocketMessage.Type.PING);
+		messageTypes.put(PongWebSocketFrame.class, WebSocketMessage.Type.PONG);
 	}
 
 
@@ -73,7 +74,7 @@ public abstract class NettyWebSocketSessionSupport<T> extends AbstractWebSocketS
 
 	protected WebSocketMessage toMessage(WebSocketFrame frame) {
 		DataBuffer payload = bufferFactory().wrap(frame.content());
-		return new WebSocketMessage(MESSAGE_TYPES.get(frame.getClass()), payload);
+		return new WebSocketMessage(messageTypes.get(frame.getClass()), payload);
 	}
 
 	protected WebSocketFrame toFrame(WebSocketMessage message) {