Polish: String function use should be optimized for single characters

spring-aop/src/main/java/org/springframework/aop/aspectj/AspectJAdviceParameterNameDiscoverer.java

@@ -421,7 +421,7 @@ public class AspectJAdviceParameterNameDiscoverer implements ParameterNameDiscov
 		String[] tokens = StringUtils.tokenizeToStringArray(this.pointcutExpression, " ");
 		for (int i = 0; i < tokens.length; i++) {
 			String toMatch = tokens[i];
-			int firstParenIndex = toMatch.indexOf("(");
+			int firstParenIndex = toMatch.indexOf('(');
 			if (firstParenIndex != -1) {
 				toMatch = toMatch.substring(0, firstParenIndex);
 			}
@@ -582,7 +582,7 @@ public class AspectJAdviceParameterNameDiscoverer implements ParameterNameDiscov
 			if (toMatch.startsWith("!")) {
 				toMatch = toMatch.substring(1);
 			}
-			int firstParenIndex = toMatch.indexOf("(");
+			int firstParenIndex = toMatch.indexOf('(');
 			if (firstParenIndex != -1) {
 				toMatch = toMatch.substring(0, firstParenIndex);
 			}

spring-aop/src/main/java/org/springframework/aop/aspectj/annotation/AspectMetadata.java

@@ -127,7 +127,7 @@ public class AspectMetadata implements Serializable {
 	 */
 	private String findPerClause(Class<?> aspectClass) {
 		String str = aspectClass.getAnnotation(Aspect.class).value();
-		str = str.substring(str.indexOf("(") + 1);
+		str = str.substring(str.indexOf('(') + 1);
 		str = str.substring(0, str.length() - 1);
 		return str;
 	}

spring-beans/src/main/java/org/springframework/beans/BeanUtils.java

@@ -367,8 +367,8 @@ public abstract class BeanUtils {
 	public static Method resolveSignature(String signature, Class<?> clazz) {
 		Assert.hasText(signature, "'signature' must not be empty");
 		Assert.notNull(clazz, "Class must not be null");
-		int firstParen = signature.indexOf("(");
-		int lastParen = signature.indexOf(")");
+		int firstParen = signature.indexOf('(');
+		int lastParen = signature.indexOf(')');
 		if (firstParen > -1 && lastParen == -1) {
 			throw new IllegalArgumentException("Invalid method signature '" + signature +
 					"': expected closing ')' for args list");

spring-beans/src/main/java/org/springframework/beans/TypeConverterDelegate.java

@@ -317,7 +317,7 @@ class TypeConverterDelegate {
 
 		if (Enum.class == requiredType && this.targetObject != null) {
 			// target type is declared as raw enum, treat the trimmed value as <enum.fqn>.FIELD_NAME
-			int index = trimmedValue.lastIndexOf(".");
+			int index = trimmedValue.lastIndexOf('.');
 			if (index > - 1) {
 				String enumType = trimmedValue.substring(0, index);
 				String fieldName = trimmedValue.substring(index + 1);

spring-beans/src/main/java/org/springframework/beans/factory/xml/BeansDtdResolver.java

@@ -58,7 +58,7 @@ public class BeansDtdResolver implements EntityResolver {
 					"] and system ID [" + systemId + "]");
 		}
 		if (systemId != null && systemId.endsWith(DTD_EXTENSION)) {
-			int lastPathSeparator = systemId.lastIndexOf("/");
+			int lastPathSeparator = systemId.lastIndexOf('/');
 			int dtdNameStart = systemId.indexOf(DTD_NAME, lastPathSeparator);
 			if (dtdNameStart != -1) {
 				String dtdFile = DTD_NAME + DTD_EXTENSION;

spring-beans/src/main/java/org/springframework/beans/factory/xml/UtilNamespaceHandler.java

@@ -88,7 +88,7 @@ public class UtilNamespaceHandler extends NamespaceHandlerSupport {
 				parserContext.getReaderContext().error("Attribute 'path' must not be empty", element);
 				return;
 			}
-			int dotIndex = path.indexOf(".");
+			int dotIndex = path.indexOf('.');
 			if (dotIndex == -1) {
 				parserContext.getReaderContext().error(
 						"Attribute 'path' must follow pattern 'beanName.propertyName'", element);

spring-core/src/main/java/org/springframework/core/env/SimpleCommandLineArgsParser.java

@@ -65,8 +65,8 @@ class SimpleCommandLineArgsParser {
 				String optionName;
 				String optionValue = null;
 				if (optionText.contains("=")) {
-					optionName = optionText.substring(0, optionText.indexOf("="));
-					optionValue = optionText.substring(optionText.indexOf("=")+1, optionText.length());
+					optionName = optionText.substring(0, optionText.indexOf('='));
+					optionValue = optionText.substring(optionText.indexOf('=')+1, optionText.length());
 				}
 				else {
 					optionName = optionText;

spring-core/src/main/java/org/springframework/core/io/support/PathMatchingResourcePatternResolver.java

@@ -290,7 +290,7 @@ public class PathMatchingResourcePatternResolver implements ResourcePatternResol
 			// Generally only look for a pattern after a prefix here,
 			// and on Tomcat only after the "*/" separator for its "war:" protocol.
 			int prefixEnd = (locationPattern.startsWith("war:") ? locationPattern.indexOf("*/") + 1 :
-					locationPattern.indexOf(":") + 1);
+					locationPattern.indexOf(':') + 1);
 			if (getPathMatcher().isPattern(locationPattern.substring(prefixEnd))) {
 				// a file pattern
 				return findPathMatchingResources(locationPattern);
@@ -531,7 +531,7 @@ public class PathMatchingResourcePatternResolver implements ResourcePatternResol
 	 * @see #retrieveMatchingFiles
 	 */
 	protected String determineRootDir(String location) {
-		int prefixEnd = location.indexOf(":") + 1;
+		int prefixEnd = location.indexOf(':') + 1;
 		int rootDirEnd = location.length();
 		while (rootDirEnd > prefixEnd && getPathMatcher().isPattern(location.substring(prefixEnd, rootDirEnd))) {
 			rootDirEnd = location.lastIndexOf('/', rootDirEnd - 2) + 1;

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

@@ -638,7 +638,7 @@ public abstract class StringUtils {
 		// first path element. This is necessary to correctly parse paths like
 		// "file:core/../core/io/Resource.class", where the ".." should just
 		// strip the first "core" directory while keeping the "file:" prefix.
-		int prefixIndex = pathToUse.indexOf(":");
+		int prefixIndex = pathToUse.indexOf(':');
 		String prefix = "";
 		if (prefixIndex != -1) {
 			prefix = pathToUse.substring(0, prefixIndex + 1);

spring-jdbc/src/main/java/org/springframework/jdbc/core/metadata/GenericCallMetaDataProvider.java

@@ -346,7 +346,7 @@ public class GenericCallMetaDataProvider implements CallMetaDataProvider {
 			else if (found.isEmpty()) {
 				if (metaDataProcedureName != null && metaDataProcedureName.contains(".") &&
 						!StringUtils.hasText(metaDataCatalogName)) {
-					String packageName = metaDataProcedureName.substring(0, metaDataProcedureName.indexOf("."));
+					String packageName = metaDataProcedureName.substring(0, metaDataProcedureName.indexOf('.'));
 					throw new InvalidDataAccessApiUsageException(
 							"Unable to determine the correct call signature for '" + metaDataProcedureName +
 							"' - package name should be specified separately using '.withCatalogName(\"" +

spring-jdbc/src/main/java/org/springframework/jdbc/datasource/init/ScriptUtils.java

@@ -210,7 +210,7 @@ public abstract class ScriptUtils {
 				}
 				else if (script.startsWith(commentPrefix, i)) {
 					// Skip over any content from the start of the comment to the EOL
-					int indexOfNextNewline = script.indexOf("\n", i);
+					int indexOfNextNewline = script.indexOf('\n', i);
 					if (indexOfNextNewline > i) {
 						i = indexOfNextNewline;
 						continue;

spring-messaging/src/main/java/org/springframework/messaging/simp/stomp/StompDecoder.java

@@ -260,7 +260,7 @@ public class StompDecoder {
 	private String unescape(String inString) {
 		StringBuilder sb = new StringBuilder(inString.length());
 		int pos = 0;  // position in the old string
-		int index = inString.indexOf("\\");
+		int index = inString.indexOf('\\');
 
 		while (index >= 0) {
 			sb.append(inString.substring(pos, index));
@@ -285,7 +285,7 @@ public class StompDecoder {
 				throw new StompConversionException("Illegal escape sequence at index " + index + ": " + inString);
 			}
 			pos = index + 2;
-			index = inString.indexOf("\\", pos);
+			index = inString.indexOf('\\', pos);
 		}
 
 		sb.append(inString.substring(pos));

spring-tx/src/main/java/org/springframework/transaction/interceptor/MethodMapTransactionAttributeSource.java

@@ -122,7 +122,7 @@ public class MethodMapTransactionAttributeSource
 	 */
 	public void addTransactionalMethod(String name, TransactionAttribute attr) {
 		Assert.notNull(name, "Name must not be null");
-		int lastDotIndex = name.lastIndexOf(".");
+		int lastDotIndex = name.lastIndexOf('.');
 		if (lastDotIndex == -1) {
 			throw new IllegalArgumentException("'" + name + "' is not a valid method name: format is FQN.methodName");
 		}

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

@@ -276,7 +276,7 @@ public class ContentDisposition {
 				}
 				else if (attribute.equals("filename*") ) {
 					filename = decodeHeaderFieldParam(value);
-					charset = Charset.forName(value.substring(0, value.indexOf("'")));
+					charset = Charset.forName(value.substring(0, value.indexOf('\'')));
 					Assert.isTrue(UTF_8.equals(charset) || ISO_8859_1.equals(charset),
 							"Charset should be UTF-8 or ISO-8859-1");
 				}
@@ -362,8 +362,8 @@ public class ContentDisposition {
 	 */
 	private static String decodeHeaderFieldParam(String input) {
 		Assert.notNull(input, "Input String should not be null");
-		int firstQuoteIndex = input.indexOf("'");
-		int secondQuoteIndex = input.indexOf("'", firstQuoteIndex + 1);
+		int firstQuoteIndex = input.indexOf('\'');
+		int secondQuoteIndex = input.indexOf('\'', firstQuoteIndex + 1);
 		// US_ASCII
 		if (firstQuoteIndex == -1 || secondQuoteIndex == -1) {
 			return input;

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

@@ -1277,7 +1277,7 @@ public class HttpHeaders implements MultiValueMap<String, String>, Serializable
 			// Let's only bother with DateTimeFormatter parsing for long enough values.
 
 			// See https://stackoverflow.com/questions/12626699/if-modified-since-http-header-passed-by-ie9-includes-length
-			int parametersIndex = headerValue.indexOf(";");
+			int parametersIndex = headerValue.indexOf(';');
 			if (parametersIndex != -1) {
 				headerValue = headerValue.substring(0, parametersIndex);
 			}

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

@@ -151,7 +151,7 @@ class DefaultPathContainer implements PathContainer {
 
 	private static void parsePathParamValues(String input, Charset charset, MultiValueMap<String, String> output) {
 		if (StringUtils.hasText(input)) {
-			int index = input.indexOf("=");
+			int index = input.indexOf('=');
 			if (index != -1) {
 				String name = input.substring(0, index);
 				String value = input.substring(index + 1);

spring-web/src/main/java/org/springframework/web/multipart/commons/CommonsMultipartFile.java

@@ -101,9 +101,9 @@ public class CommonsMultipartFile implements MultipartFile, Serializable {
 		}
 
 		// Check for Unix-style path
-		int unixSep = filename.lastIndexOf("/");
+		int unixSep = filename.lastIndexOf('/');
 		// Check for Windows-style path
-		int winSep = filename.lastIndexOf("\\");
+		int winSep = filename.lastIndexOf('\\');
 		// Cut off at latest possible point
 		int pos = (winSep > unixSep ? winSep : unixSep);
 		if (pos != -1)  {

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

@@ -769,8 +769,8 @@ public class UriComponentsBuilder implements UriBuilder, Cloneable {
 	}
 
 	private void adaptForwardedHost(String hostToUse) {
-		int portSeparatorIdx = hostToUse.lastIndexOf(":");
-		if (portSeparatorIdx > hostToUse.lastIndexOf("]")) {
+		int portSeparatorIdx = hostToUse.lastIndexOf(':');
+		if (portSeparatorIdx > hostToUse.lastIndexOf(']')) {
 			host(hostToUse.substring(0, portSeparatorIdx));
 			port(Integer.parseInt(hostToUse.substring(portSeparatorIdx + 1)));
 		}

spring-webflux/src/main/java/org/springframework/web/reactive/resource/AppCacheManifestTransformer.java

@@ -238,7 +238,7 @@ public class AppCacheManifestTransformer extends ResourceTransformerSupport {
 		}
 
 		private static boolean hasScheme(String line) {
-			int index = line.indexOf(":");
+			int index = line.indexOf(':');
 			return (line.startsWith("//") || (index > 0 && !line.substring(0, index).contains("/")));
 		}
 

spring-webflux/src/main/java/org/springframework/web/reactive/resource/CssLinkResourceTransformer.java

@@ -151,7 +151,7 @@ public class CssLinkResourceTransformer extends ResourceTransformerSupport {
 	}
 
 	private boolean hasScheme(String link) {
-		int schemeIndex = link.indexOf(":");
+		int schemeIndex = link.indexOf(':');
 		return (schemeIndex > 0 && !link.substring(0, schemeIndex).contains("/")) || link.indexOf("//") == 0;
 	}
 

spring-webflux/src/main/java/org/springframework/web/reactive/resource/ResourceUrlProvider.java

@@ -151,11 +151,11 @@ public class ResourceUrlProvider implements ApplicationListener<ContextRefreshed
 
 	private int getQueryIndex(String path) {
 		int suffixIndex = path.length();
-		int queryIndex = path.indexOf("?");
+		int queryIndex = path.indexOf('?');
 		if (queryIndex > 0) {
 			suffixIndex = queryIndex;
 		}
-		int hashIndex = path.indexOf("#");
+		int hashIndex = path.indexOf('#');
 		if (hashIndex > 0) {
 			suffixIndex = Math.min(suffixIndex, hashIndex);
 		}

spring-webflux/src/main/java/org/springframework/web/reactive/resource/WebJarsResourceResolver.java

@@ -107,7 +107,7 @@ public class WebJarsResourceResolver extends AbstractResourceResolver {
 	protected String findWebJarResourcePath(String path) {
 		try {
 			int startOffset = (path.startsWith("/") ? 1 : 0);
-			int endOffset = path.indexOf("/", 1);
+			int endOffset = path.indexOf('/', 1);
 			if (endOffset != -1) {
 				String webjar = path.substring(startOffset, endOffset);
 				String partialPath = path.substring(endOffset);

spring-webflux/src/main/java/org/springframework/web/reactive/result/view/RedirectView.java

@@ -268,7 +268,7 @@ public class RedirectView extends AbstractUrlBasedView {
 			return new StringBuilder(targetUrl);
 		}
 
-		int index = targetUrl.indexOf("#");
+		int index = targetUrl.indexOf('#');
 		String fragment = (index > -1 ? targetUrl.substring(index) : null);
 
 		StringBuilder result = new StringBuilder();

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/UrlFilenameViewController.java

@@ -140,7 +140,7 @@ public class UrlFilenameViewController extends AbstractUrlViewController {
 	 */
 	protected String extractViewNameFromUrlPath(String uri) {
 		int start = (uri.charAt(0) == '/' ? 1 : 0);
-		int lastIndex = uri.lastIndexOf(".");
+		int lastIndex = uri.lastIndexOf('.');
 		int end = (lastIndex < 0 ? uri.length() : lastIndex);
 		return uri.substring(start, end);
 	}

spring-webmvc/src/main/java/org/springframework/web/servlet/resource/AppCacheManifestTransformer.java

@@ -195,7 +195,7 @@ public class AppCacheManifestTransformer extends ResourceTransformerSupport {
 		}
 
 		private static boolean hasScheme(String line) {
-			int index = line.indexOf(":");
+			int index = line.indexOf(':');
 			return (line.startsWith("//") || (index > 0 && !line.substring(0, index).contains("/")));
 		}
 

spring-webmvc/src/main/java/org/springframework/web/servlet/resource/CssLinkResourceTransformer.java

@@ -120,7 +120,7 @@ public class CssLinkResourceTransformer extends ResourceTransformerSupport {
 	}
 
 	private boolean hasScheme(String link) {
-		int schemeIndex = link.indexOf(":");
+		int schemeIndex = link.indexOf(':');
 		return (schemeIndex > 0 && !link.substring(0, schemeIndex).contains("/")) || link.indexOf("//") == 0;
 	}
 

spring-webmvc/src/main/java/org/springframework/web/servlet/resource/ResourceHttpRequestHandler.java

@@ -355,7 +355,7 @@ public class ResourceHttpRequestHandler extends WebContentGenerator
 			Charset charset = null;
 			location = location.trim();
 			if (location.startsWith(URL_RESOURCE_CHARSET_PREFIX)) {
-				int endIndex = location.indexOf("]", URL_RESOURCE_CHARSET_PREFIX.length());
+				int endIndex = location.indexOf(']', URL_RESOURCE_CHARSET_PREFIX.length());
 				if (endIndex == -1) {
 					throw new IllegalArgumentException("Invalid charset syntax in location: " + location);
 				}

spring-webmvc/src/main/java/org/springframework/web/servlet/resource/ResourceUrlEncodingFilter.java

@@ -123,7 +123,7 @@ public class ResourceUrlEncodingFilter extends GenericFilterBean {
 		}
 
 		private int getQueryParamsIndex(String url) {
-			int index = url.indexOf("?");
+			int index = url.indexOf('?');
 			return (index > 0 ? index : url.length());
 		}
 	}

spring-webmvc/src/main/java/org/springframework/web/servlet/resource/ResourceUrlProvider.java

@@ -193,11 +193,11 @@ public class ResourceUrlProvider implements ApplicationListener<ContextRefreshed
 
 	private int getEndPathIndex(String lookupPath) {
 		int suffixIndex = lookupPath.length();
-		int queryIndex = lookupPath.indexOf("?");
+		int queryIndex = lookupPath.indexOf('?');
 		if(queryIndex > 0) {
 			suffixIndex = queryIndex;
 		}
-		int hashIndex = lookupPath.indexOf("#");
+		int hashIndex = lookupPath.indexOf('#');
 		if(hashIndex > 0) {
 			suffixIndex = Math.min(suffixIndex, hashIndex);
 		}

spring-webmvc/src/main/java/org/springframework/web/servlet/resource/WebJarsResourceResolver.java

@@ -101,7 +101,7 @@ public class WebJarsResourceResolver extends AbstractResourceResolver {
 	@Nullable
 	protected String findWebJarResourcePath(String path) {
 		int startOffset = (path.startsWith("/") ? 1 : 0);
-		int endOffset = path.indexOf("/", 1);
+		int endOffset = path.indexOf('/', 1);
 		if (endOffset != -1) {
 			String webjar = path.substring(startOffset, endOffset);
 			String partialPath = path.substring(endOffset + 1);

spring-webmvc/src/main/java/org/springframework/web/servlet/view/AbstractView.java

@@ -136,7 +136,7 @@ public abstract class AbstractView extends WebApplicationObjectSupport implement
 			StringTokenizer st = new StringTokenizer(propString, ",");
 			while (st.hasMoreTokens()) {
 				String tok = st.nextToken();
-				int eqIdx = tok.indexOf("=");
+				int eqIdx = tok.indexOf('=');
 				if (eqIdx == -1) {
 					throw new IllegalArgumentException("Expected = in attributes CSV string '" + propString + "'");
 				}