Consistently use CharSequence.isEmpty() for emptiness checks

Closes gh-33577

spring-core/src/main/java/org/springframework/cglib/core/TypeUtils.java

@@ -97,7 +97,7 @@ public class TypeUtils {
     }
 
     public static String upperFirst(String s) {
-        if (s == null || s.length() == 0) {
+        if (s == null || s.isEmpty()) {
             return s;
         }
         return Character.toUpperCase(s.charAt(0)) + s.substring(1);

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/binding/BindMarkersFactoryResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -153,7 +153,7 @@ public final class BindMarkersFactoryResolver {
 					builder.append(ch);
 				}
 			}
-			if (builder.length() == 0) {
+			if (builder.isEmpty()) {
 				return "";
 			}
 			return "_" + builder.toString();

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

@@ -877,7 +877,7 @@ public class UriComponentsBuilder implements UriBuilder, Cloneable {
 		@Override
 		@Nullable
 		public PathComponent build() {
-			if (this.path.length() == 0) {
+			if (this.path.isEmpty()) {
 				return null;
 			}
 			String sanitized = getSanitizedPath(this.path);

spring-web/src/main/java/org/springframework/web/util/pattern/CaptureVariablePathElement.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -73,7 +73,7 @@ class CaptureVariablePathElement extends PathElement {
 			return false;
 		}
 		String candidateCapture = matchingContext.pathElementValue(pathIndex);
-		if (candidateCapture.length() == 0) {
+		if (candidateCapture.isEmpty()) {
 			return false;
 		}
 

spring-web/src/main/java/org/springframework/web/util/pattern/WildcardPathElement.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -66,7 +66,7 @@ class WildcardPathElement extends PathElement {
 				}
 				else {
 					return (matchingContext.isMatchOptionalTrailingSeparator() &&  // if optional slash is on...
-							segmentData != null && segmentData.length() > 0 &&  // and there is at least one character to match the *...
+							segmentData != null && !segmentData.isEmpty() &&  // and there is at least one character to match the *...
 							(pathIndex + 1) == matchingContext.pathLength &&   // and the next path element is the end of the candidate...
 							matchingContext.isSeparator(pathIndex));  // and the final element is a separator
 				}
@@ -74,7 +74,7 @@ class WildcardPathElement extends PathElement {
 		}
 		else {
 			// Within a path (e.g. /aa/*/bb) there must be at least one character to match the wildcard
-			if (segmentData == null || segmentData.length() == 0) {
+			if (segmentData == null || segmentData.isEmpty()) {
 				return false;
 			}
 			return (this.next != null && this.next.matches(pathIndex, matchingContext));

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -323,7 +323,7 @@ public class UrlTag extends HtmlEscapingAwareTag implements ParamAware {
 		StringBuilder qs = new StringBuilder();
 		for (Param param : params) {
 			if (!usedParams.contains(param.getName()) && StringUtils.hasLength(param.getName())) {
-				if (includeQueryStringDelimiter && qs.length() == 0) {
+				if (includeQueryStringDelimiter && qs.isEmpty()) {
 					qs.append('?');
 				}
 				else {