Some very simple improvements regarding ArrayList

Author: stsypanov

spring-context-support/src/main/java/org/springframework/cache/jcache/interceptor/AbstractJCacheOperation.java

@@ -138,8 +138,9 @@ protected StringBuilder getOperationDescription() {
 
 
 	private static List<CacheParameterDetail> initializeAllParameterDetails(Method method) {
-		List<CacheParameterDetail> result = new ArrayList<>();
-		for (int i = 0; i < method.getParameterCount(); i++) {
+		int parameterCount = method.getParameterCount();
+		List<CacheParameterDetail> result = new ArrayList<>(parameterCount);
+		for (int i = 0; i < parameterCount; i++) {
 			CacheParameterDetail detail = new CacheParameterDetail(method, i);
 			result.add(detail);
 		}

spring-core/src/main/java/org/springframework/util/StringUtils.java

@@ -936,8 +936,7 @@ public static String[] mergeStringArrays(@Nullable String[] array1, @Nullable St
 			return array1;
 		}
 
-		List<String> result = new ArrayList<>();
-		result.addAll(Arrays.asList(array1));
+		List<String> result = new ArrayList<>(Arrays.asList(array1));
 		for (String str : array2) {
 			if (!result.contains(str)) {
 				result.add(str);

spring-messaging/src/main/java/org/springframework/messaging/support/MessageHeaderAccessor.java

@@ -20,6 +20,7 @@
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -373,12 +374,13 @@ public void removeHeaders(String... headerPatterns) {
 	}
 
 	private List<String> getMatchingHeaderNames(String pattern, @Nullable Map<String, Object> headers) {
+		if (headers == null) {
+			return Collections.emptyList();
+		}
 		List<String> matchingHeaderNames = new ArrayList<>();
-		if (headers != null) {
-			for (String key : headers.keySet()) {
-				if (PatternMatchUtils.simpleMatch(pattern, key)) {
-					matchingHeaderNames.add(key);
-				}
+		for (String key : headers.keySet()) {
+			if (PatternMatchUtils.simpleMatch(pattern, key)) {
+				matchingHeaderNames.add(key);
 			}
 		}
 		return matchingHeaderNames;

spring-webmvc/src/main/java/org/springframework/web/servlet/tags/form/ErrorsTag.java

@@ -317,8 +317,7 @@ protected void renderDefaultContent(TagWriter tagWriter) throws JspException {
 	 */
 	@Override
 	protected void exposeAttributes() throws JspException {
-		List<String> errorMessages = new ArrayList<>();
-		errorMessages.addAll(Arrays.asList(getBindStatus().getErrorMessages()));
+		List<String> errorMessages = new ArrayList<>(Arrays.asList(getBindStatus().getErrorMessages()));
 		this.oldMessages = this.pageContext.getAttribute(MESSAGES_ATTRIBUTE, PageContext.PAGE_SCOPE);
 		this.pageContext.setAttribute(MESSAGES_ATTRIBUTE, errorMessages, PageContext.PAGE_SCOPE);
 		this.errorMessagesWereExposed = true;