Replace string arguments with char

Optimize method calls by replacing single character String arguments
with char.

Closes gh-11680

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/cloudfoundry/Token.java

@@ -71,7 +71,7 @@ public class Token {
 	}
 
 	public byte[] getContent() {
-		return this.encoded.substring(0, this.encoded.lastIndexOf(".")).getBytes();
+		return this.encoded.substring(0, this.encoded.lastIndexOf('.')).getBytes();
 	}
 
 	public byte[] getSignature() {

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/audit/AuditEvent.java

@@ -94,7 +94,7 @@ public class AuditEvent implements Serializable {
 	private static Map<String, Object> convert(String[] data) {
 		Map<String, Object> result = new HashMap<>();
 		for (String entry : data) {
-			int index = entry.indexOf("=");
+			int index = entry.indexOf('=');
 			if (index != -1) {
 				result.put(entry.substring(0, index), entry.substring(index + 1));
 			}

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/amqp/RabbitProperties.java

@@ -891,7 +891,7 @@ public class RabbitProperties {
 		}
 
 		private String parseVirtualHost(String input) {
-			int hostIndex = input.indexOf("/");
+			int hostIndex = input.indexOf('/');
 			if (hostIndex >= 0) {
 				this.virtualHost = input.substring(hostIndex + 1);
 				if (this.virtualHost.isEmpty()) {

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/data/redis/RedisConnectionConfiguration.java

@@ -132,7 +132,7 @@ abstract class RedisConnectionConfiguration {
 			String password = null;
 			if (uri.getUserInfo() != null) {
 				password = uri.getUserInfo();
-				int index = password.lastIndexOf(":");
+				int index = password.lastIndexOf(':');
 				if (index >= 0) {
 					password = password.substring(index + 1);
 				}

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jdbc/DataSourceBeanCreationFailureAnalyzer.java

@@ -33,8 +33,8 @@ class DataSourceBeanCreationFailureAnalyzer
 	protected FailureAnalysis analyze(Throwable rootFailure,
 			DataSourceBeanCreationException cause) {
 		String message = cause.getMessage();
-		String description = message.substring(0, message.indexOf(".")).trim();
+		String description = message.substring(0, message.indexOf('.')).trim();
-		String action = message.substring(message.indexOf(".") + 1).trim();
+		String action = message.substring(message.indexOf('.') + 1).trim();
 		return new FailureAnalysis(description, action, cause);
 	}
 

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/ServerProperties.java

@@ -292,7 +292,7 @@ public class ServerProperties {
 
 		public String getServletPrefix() {
 			String result = this.path;
-			int index = result.indexOf("*");
+			int index = result.indexOf('*');
 			if (index != -1) {
 				result = result.substring(0, index);
 			}

spring-boot-project/spring-boot-cli/src/main/java/org/springframework/boot/cli/command/init/InitializrService.java

@@ -251,7 +251,7 @@ class InitializrService {
 			int start = value.indexOf(FILENAME_HEADER_PREFIX);
 			if (start != -1) {
 				value = value.substring(start + FILENAME_HEADER_PREFIX.length());
-				int end = value.indexOf("\"");
+				int end = value.indexOf('\"');
 				if (end != -1) {
 					return value.substring(0, end);
 				}

spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/RemoteUrlPropertyExtractor.java

@@ -48,7 +48,7 @@ class RemoteUrlPropertyExtractor
 		ConfigurableEnvironment environment = event.getEnvironment();
 		String url = cleanRemoteUrl(environment.getProperty(NON_OPTION_ARGS));
 		Assert.state(StringUtils.hasLength(url), "No remote URL specified");
-		Assert.state(url.indexOf(",") == -1, "Multiple URLs specified");
+		Assert.state(url.indexOf(',') == -1, "Multiple URLs specified");
 		try {
 			new URI(url);
 		}

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/context/SpringBootConfigurationFinder.java

@@ -78,7 +78,7 @@ final class SpringBootConfigurationFinder {
 	}
 
 	private String getParentPackage(String sourcePackage) {
-		int lastDot = sourcePackage.lastIndexOf(".");
+		int lastDot = sourcePackage.lastIndexOf('.');
 		return (lastDot == -1 ? "" : sourcePackage.substring(0, lastDot));
 	}
 

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/util/EnvironmentTestUtils.java

@@ -91,8 +91,8 @@ public abstract class EnvironmentTestUtils {
 	}
 
 	private static int getSeparatorIndex(String pair) {
-		int colonIndex = pair.indexOf(":");
+		int colonIndex = pair.indexOf(':');
-		int equalIndex = pair.indexOf("=");
+		int equalIndex = pair.indexOf('=');
 		if (colonIndex == -1) {
 			return equalIndex;
 		}

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/util/TestPropertyValues.java

@@ -267,8 +267,8 @@ public final class TestPropertyValues {
 		}
 
 		private static int getSeparatorIndex(String pair) {
-			int colonIndex = pair.indexOf(":");
+			int colonIndex = pair.indexOf(':');
-			int equalIndex = pair.indexOf("=");
+			int equalIndex = pair.indexOf('=');
 			if (colonIndex == -1) {
 				return equalIndex;
 			}

spring-boot-project/spring-boot-tools/spring-boot-configuration-metadata/src/main/java/org/springframework/boot/configurationmetadata/DescriptionExtractor.java

@@ -30,7 +30,7 @@ class DescriptionExtractor {
 		if (description == null) {
 			return null;
 		}
-		int dot = description.indexOf(".");
+		int dot = description.indexOf('.');
 		if (dot != -1) {
 			BreakIterator breakIterator = BreakIterator.getSentenceInstance(Locale.US);
 			breakIterator.setText(description);

spring-boot-project/spring-boot-tools/spring-boot-configuration-processor/src/main/java/org/springframework/boot/configurationprocessor/fieldvalues/javac/JavaCompilerFieldValuesParser.java

@@ -176,7 +176,7 @@ public class JavaCompilerFieldValuesParser implements FieldValuesParser {
 			Object instance = expression.getInstance();
 			if (instance != null && instance.toString().startsWith(DURATION_OF)) {
 				String type = instance.toString();
-				type = type.substring(DURATION_OF.length(), type.indexOf("("));
+				type = type.substring(DURATION_OF.length(), type.indexOf('('));
 				String suffix = DURATION_SUFFIX.get(type);
 				return (suffix == null ? null : factoryValue + suffix);
 			}

spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/JarWriter.java

@@ -253,8 +253,8 @@ public class JarWriter implements LoaderClassesWriter, AutoCloseable {
 		else {
 			entry.setUnixMode(UnixStat.FILE_FLAG | UnixStat.DEFAULT_FILE_PERM);
 		}
-		if (parent.lastIndexOf("/") != -1) {
+		if (parent.lastIndexOf('/') != -1) {
-			parent = parent.substring(0, parent.lastIndexOf("/") + 1);
+			parent = parent.substring(0, parent.lastIndexOf('/') + 1);
 			if (!parent.isEmpty()) {
 				writeEntry(new JarArchiveEntry(parent), null);
 			}

spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/PropertiesLauncher.java

@@ -498,7 +498,7 @@ public class PropertiesLauncher extends Launcher {
 			// If home dir is same as parent archive, no need to add it twice.
 			return null;
 		}
-		int index = root.indexOf("!");
+		int index = root.indexOf('!');
 		if (index != -1) {
 			File file = new File(this.home, root.substring(0, index));
 			if (root.startsWith("jar:file:")) {

spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/archive/JarFileArchive.java

@@ -112,8 +112,8 @@ public class JarFileArchive implements Archive {
 
 	private Archive getUnpackedNestedArchive(JarEntry jarEntry) throws IOException {
 		String name = jarEntry.getName();
-		if (name.lastIndexOf("/") != -1) {
+		if (name.lastIndexOf('/') != -1) {
-			name = name.substring(name.lastIndexOf("/") + 1);
+			name = name.substring(name.lastIndexOf('/') + 1);
 		}
 		File file = new File(getTempUnpackFolder(), name);
 		if (!file.exists() || file.length() != jarEntry.getSize()) {

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/BeanDefinitionLoader.java

@@ -243,7 +243,7 @@ class BeanDefinitionLoader {
 			// a file list of the package content. We double check here that it's not
 			// actually a package.
 			String path = ((ClassPathResource) resource).getPath();
-			if (path.indexOf(".") == -1) {
+			if (path.indexOf('.') == -1) {
 				try {
 					return Package.getPackage(path) == null;
 				}

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/diagnostics/analyzer/NoUniqueBeanDefinitionFailureAnalyzer.java

@@ -93,7 +93,7 @@ class NoUniqueBeanDefinitionFailureAnalyzer
 	private String[] extractBeanNames(NoUniqueBeanDefinitionException cause) {
 		if (cause.getMessage().indexOf("but found") > -1) {
 			return StringUtils.commaDelimitedListToStringArray(cause.getMessage()
-					.substring(cause.getMessage().lastIndexOf(":") + 1).trim());
+					.substring(cause.getMessage().lastIndexOf(':') + 1).trim());
 		}
 		return null;
 	}

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

@@ -69,7 +69,7 @@ class SpringPropertyAction extends Action {
 		if (value != null) {
 			return value;
 		}
-		int lastDot = source.lastIndexOf(".");
+		int lastDot = source.lastIndexOf('.');
 		if (lastDot > 0) {
 			String prefix = source.substring(0, lastDot + 1);
 			return this.environment.getProperty(prefix + source.substring(lastDot + 1),