Avoid string concatenation inside StringBuilder append()

See gh-15589

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/endpoint/jmx/annotation/DiscoveredJmxOperation.java

@@ -180,9 +180,9 @@ class DiscoveredJmxOperation extends AbstractDiscoveredOperation implements JmxO
 		public String toString() {
 			StringBuilder result = new StringBuilder(this.name);
 			if (this.description != null) {
-				result.append(" (" + this.description + ")");
+				result.append(" (").append(this.description).append(")");
 			}
-			result.append(":" + this.type);
+			result.append(":").append(this.type);
 			return result.toString();
 		}
 

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/endpoint/web/WebOperationRequestPredicate.java

@@ -124,12 +124,12 @@ public final class WebOperationRequestPredicate {
 		StringBuilder result = new StringBuilder(
 				this.httpMethod + " to path '" + this.path + "'");
 		if (!CollectionUtils.isEmpty(this.consumes)) {
-			result.append(" consumes: "
-					+ StringUtils.collectionToCommaDelimitedString(this.consumes));
+			result.append(" consumes: ")
+					.append(StringUtils.collectionToCommaDelimitedString(this.consumes));
 		}
 		if (!CollectionUtils.isEmpty(this.produces)) {
-			result.append(" produces: "
-					+ StringUtils.collectionToCommaDelimitedString(this.produces));
+			result.append(" produces: ")
+					.append(StringUtils.collectionToCommaDelimitedString(this.produces));
 		}
 		return result.toString();
 	}

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/ConditionMessage.java

@@ -386,14 +386,14 @@ public final class ConditionMessage {
 			items = style.applyTo(items);
 			if ((this.condition == null || items.size() <= 1)
 					&& StringUtils.hasLength(this.singular)) {
-				message.append(" " + this.singular);
+				message.append(" ").append(this.singular);
 			}
 			else if (StringUtils.hasLength(this.plural)) {
-				message.append(" " + this.plural);
+				message.append(" ").append(this.plural);
 			}
 			if (items != null && !items.isEmpty()) {
-				message.append(
-						" " + StringUtils.collectionToDelimitedString(items, ", "));
+				message.append(" ")
+						.append(StringUtils.collectionToDelimitedString(items, ", "));
 			}
 			return this.condition.because(message.toString());
 		}

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

@@ -66,9 +66,9 @@ class ServiceCapabilitiesReportGenerator {
 	private String generateHelp(String url, InitializrServiceMetadata metadata) {
 		String header = "Capabilities of " + url;
 		StringBuilder report = new StringBuilder();
-		report.append(repeat("=", header.length()) + NEW_LINE);
-		report.append(header + NEW_LINE);
-		report.append(repeat("=", header.length()) + NEW_LINE);
+		report.append(repeat("=", header.length())).append(NEW_LINE);
+		report.append(header).append(NEW_LINE);
+		report.append(repeat("=", header.length())).append(NEW_LINE);
 		report.append(NEW_LINE);
 		reportAvailableDependencies(metadata, report);
 		report.append(NEW_LINE);
@@ -80,13 +80,13 @@ class ServiceCapabilitiesReportGenerator {
 
 	private void reportAvailableDependencies(InitializrServiceMetadata metadata,
 			StringBuilder report) {
-		report.append("Available dependencies:" + NEW_LINE);
-		report.append("-----------------------" + NEW_LINE);
+		report.append("Available dependencies:").append(NEW_LINE);
+		report.append("-----------------------").append(NEW_LINE);
 		List<Dependency> dependencies = getSortedDependencies(metadata);
 		for (Dependency dependency : dependencies) {
-			report.append(dependency.getId() + " - " + dependency.getName());
+			report.append(dependency.getId()).append(" - ").append(dependency.getName());
 			if (dependency.getDescription() != null) {
-				report.append(": " + dependency.getDescription());
+				report.append(": ").append(dependency.getDescription());
 			}
 			report.append(NEW_LINE);
 		}
@@ -100,14 +100,14 @@ class ServiceCapabilitiesReportGenerator {
 
 	private void reportAvailableProjectTypes(InitializrServiceMetadata metadata,
 			StringBuilder report) {
-		report.append("Available project types:" + NEW_LINE);
-		report.append("------------------------" + NEW_LINE);
+		report.append("Available project types:").append(NEW_LINE);
+		report.append("------------------------").append(NEW_LINE);
 		SortedSet<Entry<String, ProjectType>> entries = new TreeSet<>(
 				Comparator.comparing(Entry::getKey));
 		entries.addAll(metadata.getProjectTypes().entrySet());
 		for (Entry<String, ProjectType> entry : entries) {
 			ProjectType type = entry.getValue();
-			report.append(entry.getKey() + " -  " + type.getName());
+			report.append(entry.getKey()).append(" -  ").append(type.getName());
 			if (!type.getTags().isEmpty()) {
 				reportTags(report, type);
 			}
@@ -124,7 +124,7 @@ class ServiceCapabilitiesReportGenerator {
 		report.append(" [");
 		while (iterator.hasNext()) {
 			Map.Entry<String, String> entry = iterator.next();
-			report.append(entry.getKey() + ":" + entry.getValue());
+			report.append(entry.getKey()).append(":").append(entry.getValue());
 			if (iterator.hasNext()) {
 				report.append(", ");
 			}
@@ -134,13 +134,14 @@ class ServiceCapabilitiesReportGenerator {
 
 	private void reportDefaults(StringBuilder report,
 			InitializrServiceMetadata metadata) {
-		report.append("Defaults:" + NEW_LINE);
-		report.append("---------" + NEW_LINE);
+		report.append("Defaults:").append(NEW_LINE);
+		report.append("---------").append(NEW_LINE);
 		List<String> defaultsKeys = new ArrayList<>(metadata.getDefaults().keySet());
 		Collections.sort(defaultsKeys);
 		for (String defaultsKey : defaultsKeys) {
 			String defaultsValue = metadata.getDefaults().get(defaultsKey);
-			report.append(defaultsKey + ": " + defaultsValue + NEW_LINE);
+			report.append(defaultsKey).append(": ").append(defaultsValue)
+					.append(NEW_LINE);
 		}
 	}
 

spring-boot-project/spring-boot-tools/spring-boot-configuration-processor/src/test/java/org/springframework/boot/configurationprocessor/metadata/Metadata.java

@@ -108,7 +108,7 @@ public final class Metadata {
 
 		private String createDescription() {
 			StringBuilder description = new StringBuilder();
-			description.append("an item named '" + this.name + "'");
+			description.append("an item named '").append(this.name).append("'");
 			if (this.type != null) {
 				description.append(" with dataType:").append(this.type);
 			}
@@ -258,7 +258,7 @@ public final class Metadata {
 
 		private String createDescription() {
 			StringBuilder description = new StringBuilder();
-			description.append("a hints name '" + this.name + "'");
+			description.append("a hints name '").append(this.name).append("'");
 			if (!this.valueConditions.isEmpty()) {
 				description.append(" with values:").append(this.valueConditions);
 			}
@@ -348,7 +348,7 @@ public final class Metadata {
 
 		private String createDescription() {
 			StringBuilder description = new StringBuilder();
-			description.append("value hint at index '" + this.index + "'");
+			description.append("value hint at index '").append(this.index).append("'");
 			if (this.value != null) {
 				description.append(" with value:").append(this.value);
 			}

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/plugin/UnresolvedDependenciesAnalyzer.java

@@ -52,11 +52,11 @@ class UnresolvedDependenciesAnalyzer {
 			StringBuilder message = new StringBuilder();
 			message.append("\nDuring the build, one or more dependencies that were "
 					+ "declared without a version failed to resolve:\n");
-			this.dependenciesWithNoVersion
-					.forEach((dependency) -> message.append("    " + dependency + "\n"));
+			this.dependenciesWithNoVersion.forEach((dependency) -> message.append("    ")
+					.append(dependency).append("\n"));
 			message.append("\nDid you forget to apply the "
-					+ "io.spring.dependency-management plugin to the " + project.getName()
-					+ " project?\n");
+					+ "io.spring.dependency-management plugin to the ");
+			message.append(project.getName()).append(" project?\n");
 			logger.warn(message.toString());
 		}
 	}

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

@@ -88,7 +88,7 @@ class StartupInfoLogger {
 		message.append(stopWatch.getTotalTimeSeconds());
 		try {
 			double uptime = ManagementFactory.getRuntimeMXBean().getUptime() / 1000.0;
-			message.append(" seconds (JVM running for " + uptime + ")");
+			message.append(" seconds (JVM running for ").append(uptime).append(")");
 		}
 		catch (Throwable ex) {
 			// No JVM time available

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/ConfigurationPropertiesBindException.java

@@ -58,8 +58,8 @@ public class ConfigurationPropertiesBindException extends BeanCreationException
 
 	private static String getMessage(Object bean, ConfigurationProperties annotation) {
 		StringBuilder message = new StringBuilder();
-		message.append("Could not bind properties to '"
-				+ ClassUtils.getShortName(bean.getClass()) + "' : ");
+		message.append("Could not bind properties to '");
+		message.append(ClassUtils.getShortName(bean.getClass())).append("' : ");
 		message.append("prefix=").append(annotation.prefix());
 		message.append(", ignoreInvalidFields=").append(annotation.ignoreInvalidFields());
 		message.append(", ignoreUnknownFields=").append(annotation.ignoreUnknownFields());

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/validation/BindValidationException.java

@@ -48,7 +48,7 @@ public class BindValidationException extends RuntimeException {
 	private static String getMessage(ValidationErrors errors) {
 		StringBuilder message = new StringBuilder("Binding validation errors");
 		if (errors != null) {
-			message.append(" on " + errors.getName());
+			message.append(" on ").append(errors.getName());
 			errors.getAllErrors().forEach(
 					(error) -> message.append(String.format("%n   - %s", error)));
 		}

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

@@ -84,8 +84,9 @@ class InvalidConfigurationPropertyValueFailureAnalyzer
 			InvalidConfigurationPropertyValueException cause,
 			List<Descriptor> descriptors) {
 		Descriptor mainDescriptor = descriptors.get(0);
-		message.append("Invalid value '" + mainDescriptor.getValue()
-				+ "' for configuration property '" + cause.getName() + "'");
+		message.append("Invalid value '").append(mainDescriptor.getValue())
+				.append("' for configuration property '");
+		message.append(cause.getName()).append("'");
 		mainDescriptor.appendOrigin(message);
 		message.append(".");
 	}
@@ -111,8 +112,8 @@ class InvalidConfigurationPropertyValueFailureAnalyzer
 							+ "property %s:%n%n",
 					(others.size() > 1) ? "sources" : "source"));
 			for (Descriptor other : others) {
-				message.append("\t- In '" + other.getPropertySource() + "'");
-				message.append(" with the value '" + other.getValue() + "'");
+				message.append("\t- In '").append(other.getPropertySource()).append("'");
+				message.append(" with the value '").append(other.getValue()).append("'");
 				other.appendOrigin(message);
 				message.append(String.format(".%n"));
 			}
@@ -153,7 +154,7 @@ class InvalidConfigurationPropertyValueFailureAnalyzer
 
 		public void appendOrigin(StringBuilder message) {
 			if (this.origin != null) {
-				message.append(" (originating from '" + this.origin + "')");
+				message.append(" (originating from '").append(this.origin).append("')");
 			}
 		}
 

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/env/YamlPropertySourceLoaderTests.java

@@ -55,7 +55,7 @@ public class YamlPropertySourceLoaderTests {
 		StringBuilder yaml = new StringBuilder();
 		List<String> expected = new ArrayList<>();
 		for (char c = 'a'; c <= 'z'; c++) {
-			yaml.append(c + ": value" + c + "\n");
+			yaml.append(c).append(": value").append(c).append("\n");
 			expected.add(String.valueOf(c));
 		}
 		ByteArrayResource resource = new ByteArrayResource(yaml.toString().getBytes());

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/servlet/server/AbstractServletWebServerFactoryTests.java

@@ -1260,7 +1260,8 @@ public abstract class AbstractServletWebServerFactoryTests {
 						Object existing = session.getAttribute("boot");
 						session.setAttribute("boot", value);
 						PrintWriter writer = response.getWriter();
-						writer.append(String.valueOf(existing) + ":" + value);
+						writer.append(String.valueOf(existing)).append(":")
+								.append(String.valueOf(value));
 					}
 
 				}, "/session");