Replace some String.length() checks with String.isEmpty()

Closes gh-10451

spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/endpoint/jmx/DefaultEndpointObjectNameFactory.java

@@ -66,7 +66,7 @@ class DefaultEndpointObjectNameFactory implements EndpointObjectNameFactory {
 
 	private boolean hasMBean(String baseObjectName) throws MalformedObjectNameException {
 		ObjectName query = new ObjectName(baseObjectName + ",*");
-		return this.mBeanServer.queryNames(query, null).size() > 0;
+		return !this.mBeanServer.queryNames(query, null).isEmpty();
 	}
 
 	private String getStaticNames() {

spring-boot-cli/src/main/java/org/springframework/boot/cli/command/archive/ResourceMatcher.java

@@ -117,7 +117,7 @@ class ResourceMatcher {
 				value = value.substring(1);
 				minus.add(value);
 			}
-			else if (value.trim().length() > 0) {
+			else if (!value.trim().isEmpty()) {
 				result.add(value);
 			}
 		}

spring-boot-cli/src/main/java/org/springframework/boot/cli/command/core/HintCommand.java

@@ -57,7 +57,7 @@ public class HintCommand extends AbstractCommand {
 			if (index == 0) {
 				showCommandHints(starting);
 			}
-			else if (!arguments.isEmpty() && (starting.length() > 0)) {
+			else if (!arguments.isEmpty() && !starting.isEmpty()) {
 				String command = arguments.remove(0);
 				showCommandOptionHints(command, Collections.unmodifiableList(arguments),
 						starting);

spring-boot-test-autoconfigure/src/main/java/org/springframework/boot/test/autoconfigure/web/client/MockRestServiceServerAutoConfiguration.java

@@ -113,7 +113,7 @@ public class MockRestServiceServerAutoConfiguration {
 		private RequestExpectationManager getDelegate() {
 			Map<RestTemplate, RequestExpectationManager> expectationManagers = this.customizer
 					.getExpectationManagers();
-			Assert.state(expectationManagers.size() > 0,
+			Assert.state(!expectationManagers.isEmpty(),
 					"Unable to use auto-configured MockRestServiceServer since "
 							+ "MockServerRestTemplateCustomizer has not been bound to "
 							+ "a RestTemplate");

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

@@ -63,7 +63,7 @@ final class SpringBootConfigurationFinder {
 	}
 
 	private Class<?> scanPackage(String source) {
-		while (source.length() > 0) {
+		while (!source.isEmpty()) {
 			Set<BeanDefinition> components = this.scanner.findCandidateComponents(source);
 			if (!components.isEmpty()) {
 				Assert.state(components.size() == 1,

spring-boot-test/src/main/java/org/springframework/boot/test/web/client/MockServerRestTemplateCustomizer.java

@@ -98,7 +98,7 @@ public class MockServerRestTemplateCustomizer implements RestTemplateCustomizer
 	}
 
 	public MockRestServiceServer getServer() {
-		Assert.state(this.servers.size() > 0,
+		Assert.state(!this.servers.isEmpty(),
 				"Unable to return a single MockRestServiceServer since "
 						+ "MockServerRestTemplateCustomizer has not been bound to "
 						+ "a RestTemplate");

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

@@ -88,7 +88,7 @@ class RawConfigurationMetadata {
 	}
 
 	private static boolean hasLength(String string) {
-		return (string != null && string.length() > 0);
+		return (string != null && !string.isEmpty());
 	}
 
 }

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

@@ -63,7 +63,7 @@ class UnresolvedDependenciesAnalyzer {
 
 	private boolean hasNoVersion(ModuleVersionSelector selector) {
 		String version = selector.getVersion();
-		return version == null || version.trim().length() == 0;
+		return version == null || version.trim().isEmpty();
 	}
 
 }

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

@@ -255,7 +255,7 @@ public class JarWriter implements LoaderClassesWriter, AutoCloseable {
 		}
 		if (parent.lastIndexOf("/") != -1) {
 			parent = parent.substring(0, parent.lastIndexOf("/") + 1);
-			if (parent.length() > 0) {
+			if (!parent.isEmpty()) {
 				writeEntry(new JarArchiveEntry(parent), null);
 			}
 		}

spring-boot-tools/spring-boot-maven-plugin/src/main/java/org/springframework/boot/maven/AbstractRunMojo.java

@@ -201,7 +201,7 @@ public abstract class AbstractRunMojo extends AbstractDependencyFilterMojo {
 	}
 
 	private boolean hasJvmArgs() {
-		return (this.jvmArguments != null && this.jvmArguments.length() > 0);
+		return (this.jvmArguments != null && !this.jvmArguments.isEmpty());
 	}
 
 	private boolean hasWorkingDirectorySet() {

spring-boot-tools/spring-boot-maven-plugin/src/main/java/org/springframework/boot/maven/RepackageMojo.java

@@ -225,7 +225,7 @@ public class RepackageMojo extends AbstractDependencyFilterMojo {
 
 	private File getTargetFile() {
 		String classifier = (this.classifier == null ? "" : this.classifier.trim());
-		if (classifier.length() > 0 && !classifier.startsWith("-")) {
+		if (!classifier.isEmpty() && !classifier.startsWith("-")) {
 			classifier = "-" + classifier;
 		}
 		if (!this.outputDirectory.exists()) {
@@ -292,7 +292,7 @@ public class RepackageMojo extends AbstractDependencyFilterMojo {
 			String... valueCandidates) {
 		if (!properties.containsKey(key)) {
 			for (String candidate : valueCandidates) {
-				if (candidate != null && candidate.length() > 0) {
+				if (candidate != null && !candidate.isEmpty()) {
 					properties.put(key, candidate);
 					return;
 				}

spring-boot/src/main/java/org/springframework/boot/json/BasicJsonParser.java

@@ -93,14 +93,14 @@ public class BasicJsonParser implements JsonParser {
 	}
 
 	private static String trimTrailingCharacter(String string, char c) {
-		if (string.length() > 0 && string.charAt(string.length() - 1) == c) {
+		if (!string.isEmpty() && string.charAt(string.length() - 1) == c) {
 			return string.substring(0, string.length() - 1);
 		}
 		return string;
 	}
 
 	private static String trimLeadingCharacter(String string, char c) {
-		if (string.length() > 0 && string.charAt(0) == c) {
+		if (!string.isEmpty() && string.charAt(0) == c) {
 			return string.substring(1);
 		}
 		return string;

spring-boot/src/main/java/org/springframework/boot/web/servlet/server/AbstractServletWebServerFactory.java

@@ -125,7 +125,7 @@ public abstract class AbstractServletWebServerFactory
 
 	private void checkContextPath(String contextPath) {
 		Assert.notNull(contextPath, "ContextPath must not be null");
-		if (contextPath.length() > 0) {
+		if (!contextPath.isEmpty()) {
 			if ("/".equals(contextPath)) {
 				throw new IllegalArgumentException(
 						"Root ContextPath must be specified using an empty string");