Remove unnecessary field initialization

Closes gh-45168

Co-authored-by: CatiaCorreia catia.correia97@gmail.com

buildSrc/src/main/java/org/springframework/boot/build/mavenplugin/PluginXmlParser.java

@@ -142,7 +142,7 @@ class PluginXmlParser {
 
 			return new Iterator<>() {
 
-				private int index = 0;
+				private int index;
 
 				@Override
 				public boolean hasNext() {

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/jdbc/DataSourceHealthIndicatorProperties.java

@@ -32,7 +32,7 @@ public class DataSourceHealthIndicatorProperties {
 	 * Whether to ignore AbstractRoutingDataSources when creating database health
 	 * indicators.
 	 */
-	private boolean ignoreRoutingDataSources = false;
+	private boolean ignoreRoutingDataSources;
 
 	public boolean isIgnoreRoutingDataSources() {
 		return this.ignoreRoutingDataSources;

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/export/elastic/ElasticProperties.java

@@ -83,7 +83,7 @@ public class ElasticProperties extends StepRegistryProperties {
 	 * Whether to enable _source in the default index template when auto-creating the
 	 * index.
 	 */
-	private boolean enableSource = false;
+	private boolean enableSource;
 
 	public String getHost() {
 		return this.host;

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/export/stackdriver/StackdriverProperties.java

@@ -52,7 +52,7 @@ public class StackdriverProperties extends StepRegistryProperties {
 	 * published as the GAUGE MetricKind. When true, counter metrics are published as the
 	 * CUMULATIVE MetricKind.
 	 */
-	private boolean useSemanticMetricTypes = false;
+	private boolean useSemanticMetricTypes;
 
 	/**
 	 * Prefix for metric type. Valid prefixes are described in the Google Cloud

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/tracing/TracingProperties.java

@@ -281,7 +281,7 @@ public class TracingProperties {
 		 * between client and server spans. Requires B3 propagation and a compatible
 		 * backend.
 		 */
-		private boolean spanJoiningSupported = false;
+		private boolean spanJoiningSupported;
 
 		public boolean isSpanJoiningSupported() {
 			return this.spanJoiningSupported;

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/context/properties/ConfigurationPropertiesReportEndpointTests.java

@@ -464,7 +464,7 @@ class ConfigurationPropertiesReportEndpointTests {
 
 		private String myTestProperty = "654321";
 
-		private String nullValue = null;
+		private String nullValue;
 
 		private Duration duration = Duration.ofSeconds(10);
 

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

@@ -936,7 +936,7 @@ public class RabbitProperties {
 		 * Whether to fail if the queues declared by the container are not available on
 		 * the broker.
 		 */
-		private boolean missingQueuesFatal = false;
+		private boolean missingQueuesFatal;
 
 		public Integer getConsumersPerQueue() {
 			return this.consumersPerQueue;

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/context/MessageSourceProperties.java

@@ -74,13 +74,13 @@ public class MessageSourceProperties {
 	 * Whether to always apply the MessageFormat rules, parsing even messages without
 	 * arguments.
 	 */
-	private boolean alwaysUseMessageFormat = false;
+	private boolean alwaysUseMessageFormat;
 
 	/**
 	 * Whether to use the message code as the default message instead of throwing a
 	 * "NoSuchMessageException". Recommended during development only.
 	 */
-	private boolean useCodeAsDefaultMessage = false;
+	private boolean useCodeAsDefaultMessage;
 
 	public List<String> getBasename() {
 		return this.basename;

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/data/jpa/JpaRepositoriesRegistrar.java

@@ -38,7 +38,7 @@ import org.springframework.util.StringUtils;
  */
 class JpaRepositoriesRegistrar extends AbstractRepositoryConfigurationSourceSupport {
 
-	private BootstrapMode bootstrapMode = null;
+	private BootstrapMode bootstrapMode;
 
 	@Override
 	protected Class<? extends Annotation> getAnnotation() {

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

@@ -39,7 +39,7 @@ public class RedisProperties {
 	/**
 	 * Database index used by the connection factory.
 	 */
-	private int database = 0;
+	private int database;
 
 	/**
 	 * Connection URL. Overrides host, port, username, and password. Example:
@@ -245,7 +245,7 @@ public class RedisProperties {
 		 * setting only has an effect if both it and time between eviction runs are
 		 * positive.
 		 */
-		private int minIdle = 0;
+		private int minIdle;
 
 		/**
 		 * Maximum number of connections that can be allocated by the pool at a given

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

@@ -60,7 +60,7 @@ public class SpringDataWebProperties {
 		 * Whether to expose and assume 1-based page number indexes. Defaults to "false",
 		 * meaning a page number of 0 in the request equals the first page.
 		 */
-		private boolean oneIndexedParameters = false;
+		private boolean oneIndexedParameters;
 
 		/**
 		 * General prefix to be prepended to the page number and page size parameters.

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/elasticsearch/ElasticsearchProperties.java

@@ -60,7 +60,7 @@ public class ElasticsearchProperties {
 	/**
 	 * Whether to enable socket keep alive between client and Elasticsearch.
 	 */
-	private boolean socketKeepAlive = false;
+	private boolean socketKeepAlive;
 
 	/**
 	 * Prefix added to the path of every request sent to Elasticsearch.

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/flyway/FlywayMigrationInitializer.java

@@ -35,7 +35,7 @@ public class FlywayMigrationInitializer implements InitializingBean, Ordered {
 
 	private final FlywayMigrationStrategy migrationStrategy;
 
-	private int order = 0;
+	private int order;
 
 	/**
 	 * Create a new {@link FlywayMigrationInitializer} instance.

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/flyway/FlywayProperties.java

@@ -247,7 +247,7 @@ public class FlywayProperties {
 	 * Whether to validate migrations and callbacks whose scripts do not obey the correct
 	 * naming convention.
 	 */
-	private boolean validateMigrationNaming = false;
+	private boolean validateMigrationNaming;
 
 	/**
 	 * Whether to automatically call validate when performing a migration.

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/graphql/GraphQlProperties.java

@@ -166,7 +166,7 @@ public class GraphQlProperties {
 			 * Whether the endpoint that prints the schema is enabled. Schema is available
 			 * under spring.graphql.path + "/schema".
 			 */
-			private boolean enabled = false;
+			private boolean enabled;
 
 			public boolean isEnabled() {
 				return this.enabled;
@@ -190,7 +190,7 @@ public class GraphQlProperties {
 		/**
 		 * Whether the default GraphiQL UI is enabled.
 		 */
-		private boolean enabled = false;
+		private boolean enabled;
 
 		public String getPath() {
 			return this.path;

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/h2/H2ConsoleProperties.java

@@ -38,7 +38,7 @@ public class H2ConsoleProperties {
 	/**
 	 * Whether to enable the console.
 	 */
-	private boolean enabled = false;
+	private boolean enabled;
 
 	private final Settings settings = new Settings();
 
@@ -70,12 +70,12 @@ public class H2ConsoleProperties {
 		/**
 		 * Whether to enable trace output.
 		 */
-		private boolean trace = false;
+		private boolean trace;
 
 		/**
 		 * Whether to enable remote access.
 		 */
-		private boolean webAllowOthers = false;
+		private boolean webAllowOthers;
 
 		/**
 		 * Password to access preferences and tools of H2 Console.

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/integration/IntegrationProperties.java

@@ -127,7 +127,7 @@ public class IntegrationProperties {
 		 * Whether to throw an exception when a reply is not expected anymore by a
 		 * gateway.
 		 */
-		private boolean throwExceptionOnLateReply = false;
+		private boolean throwExceptionOnLateReply;
 
 		/**
 		 * List of message header names that should not be populated into Message

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jackson/JacksonProperties.java

@@ -110,7 +110,7 @@ public class JacksonProperties {
 	 * Time zone used when formatting dates. For instance, "America/Los_Angeles" or
 	 * "GMT+10".
 	 */
-	private TimeZone timeZone = null;
+	private TimeZone timeZone;
 
 	/**
 	 * Locale used for formatting.

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jms/JmsProperties.java

@@ -37,7 +37,7 @@ public class JmsProperties {
 	/**
 	 * Whether the default destination type is topic.
 	 */
-	private boolean pubSubDomain = false;
+	private boolean pubSubDomain;
 
 	/**
 	 * Connection factory JNDI name. When set, takes precedence to others connection
@@ -48,7 +48,7 @@ public class JmsProperties {
 	/**
 	 * Whether the subscription is durable.
 	 */
-	private boolean subscriptionDurable = false;
+	private boolean subscriptionDurable;
 
 	/**
 	 * Client id of the connection.
@@ -115,7 +115,7 @@ public class JmsProperties {
 		/**
 		 * Whether to cache message consumers.
 		 */
-		private boolean consumers = false;
+		private boolean consumers;
 
 		/**
 		 * Whether to cache message producers.
@@ -423,7 +423,7 @@ public class JmsProperties {
 			/**
 			 * Whether to use transacted sessions.
 			 */
-			private boolean transacted = false;
+			private boolean transacted;
 
 			public AcknowledgeMode getAcknowledgeMode() {
 				return this.acknowledgeMode;

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jms/activemq/ActiveMQProperties.java

@@ -67,7 +67,7 @@ public class ActiveMQProperties {
 	 * Whether to stop message delivery before re-delivering messages from a rolled back
 	 * transaction. This implies that message order is not preserved when this is enabled.
 	 */
-	private boolean nonBlockingRedelivery = false;
+	private boolean nonBlockingRedelivery;
 
 	/**
 	 * Time to wait on message sends for a response. Set it to 0 to wait forever.

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jmx/JmxProperties.java

@@ -31,12 +31,12 @@ public class JmxProperties {
 	/**
 	 * Expose Spring's management beans to the JMX domain.
 	 */
-	private boolean enabled = false;
+	private boolean enabled;
 
 	/**
 	 * Whether unique runtime object names should be ensured.
 	 */
-	private boolean uniqueNames = false;
+	private boolean uniqueNames;
 
 	/**
 	 * MBeanServer bean name.

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/kafka/KafkaProperties.java

@@ -1057,13 +1057,13 @@ public class KafkaProperties {
 		 * Whether the container should fail to start if at least one of the configured
 		 * topics are not present on the broker.
 		 */
-		private boolean missingTopicsFatal = false;
+		private boolean missingTopicsFatal;
 
 		/**
 		 * Whether the container stops after the current record is processed or after all
 		 * the records from the previous poll are processed.
 		 */
-		private boolean immediateStop = false;
+		private boolean immediateStop;
 
 		/**
 		 * Whether to auto start the container.
@@ -1658,7 +1658,7 @@ public class KafkaProperties {
 				/**
 				 * Multiplier to use for generating the next backoff delay.
 				 */
-				private double multiplier = 0.0;
+				private double multiplier;
 
 				/**
 				 * Maximum wait between retries. If less than the delay then the default
@@ -1669,7 +1669,7 @@ public class KafkaProperties {
 				/**
 				 * Whether to have the backoff delays.
 				 */
-				private boolean random = false;
+				private boolean random;
 
 				public Duration getDelay() {
 					return this.delay;
@@ -1714,12 +1714,12 @@ public class KafkaProperties {
 		/**
 		 * Cleanup the application’s local state directory on startup.
 		 */
-		private boolean onStartup = false;
+		private boolean onStartup;
 
 		/**
 		 * Cleanup the application’s local state directory on shutdown.
 		 */
-		private boolean onShutdown = false;
+		private boolean onShutdown;
 
 		public boolean isOnStartup() {
 			return this.onStartup;

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/ldap/LdapProperties.java

@@ -142,13 +142,13 @@ public class LdapProperties {
 		 * Whether PartialResultException should be ignored in searches through the
 		 * LdapTemplate.
 		 */
-		private boolean ignorePartialResultException = false;
+		private boolean ignorePartialResultException;
 
 		/**
 		 * Whether NameNotFoundException should be ignored in searches through the
 		 * LdapTemplate.
 		 */
-		private boolean ignoreNameNotFoundException = false;
+		private boolean ignoreNameNotFoundException;
 
 		/**
 		 * Whether SizeLimitExceededException should be ignored in searches through the

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/ldap/embedded/EmbeddedLdapProperties.java

@@ -37,7 +37,7 @@ public class EmbeddedLdapProperties {
 	/**
 	 * Embedded LDAP port.
 	 */
-	private int port = 0;
+	private int port;
 
 	/**
 	 * Embedded LDAP credentials.

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mail/MailProperties.java

@@ -151,7 +151,7 @@ public class MailProperties {
 		 * Whether to enable SSL support. If enabled, 'mail.(protocol).ssl.enable'
 		 * property is set to 'true'.
 		 */
-		private boolean enabled = false;
+		private boolean enabled;
 
 		/**
 		 * SSL bundle name. If set, 'mail.(protocol).ssl.socketFactory' property is set to

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mongo/MongoProperties.java

@@ -59,7 +59,7 @@ public class MongoProperties {
 	/**
 	 * Mongo server port. Ignored if 'uri' is set.
 	 */
-	private Integer port = null;
+	private Integer port;
 
 	/**
 	 * Additional server hosts. Ignored if 'uri' is set or if 'host' is omitted.

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mongo/StandardMongoClientSettingsBuilderCustomizer.java

@@ -45,7 +45,7 @@ public class StandardMongoClientSettingsBuilderCustomizer implements MongoClient
 
 	private final SslBundles sslBundles;
 
-	private int order = 0;
+	private int order;
 
 	public StandardMongoClientSettingsBuilderCustomizer(ConnectionString connectionString,
 			UuidRepresentation uuidRepresentation, MongoProperties.Ssl ssl, SslBundles sslBundles) {

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mustache/MustacheProperties.java

@@ -157,13 +157,13 @@ public class MustacheProperties {
 		 * Whether HttpServletRequest attributes are allowed to override (hide) controller
 		 * generated model attributes of the same name.
 		 */
-		private boolean allowRequestOverride = false;
+		private boolean allowRequestOverride;
 
 		/**
 		 * Whether HttpSession attributes are allowed to override (hide) controller
 		 * generated model attributes of the same name.
 		 */
-		private boolean allowSessionOverride = false;
+		private boolean allowSessionOverride;
 
 		/**
 		 * Whether to enable template caching.
@@ -179,13 +179,13 @@ public class MustacheProperties {
 		 * Whether all request attributes should be added to the model prior to merging
 		 * with the template.
 		 */
-		private boolean exposeRequestAttributes = false;
+		private boolean exposeRequestAttributes;
 
 		/**
 		 * Whether all HttpSession attributes should be added to the model prior to
 		 * merging with the template.
 		 */
-		private boolean exposeSessionAttributes = false;
+		private boolean exposeSessionAttributes;
 
 		/**
 		 * Whether to expose a RequestContext for use by Spring's macro library, under the

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/neo4j/Neo4jProperties.java

@@ -151,12 +151,12 @@ public class Neo4jProperties {
 		/**
 		 * Whether to enable metrics.
 		 */
-		private boolean metricsEnabled = false;
+		private boolean metricsEnabled;
 
 		/**
 		 * Whether to log leaked sessions.
 		 */
-		private boolean logLeakedSessions = false;
+		private boolean logLeakedSessions;
 
 		/**
 		 * Maximum amount of connections in the connection pool towards a single database.
@@ -236,7 +236,7 @@ public class Neo4jProperties {
 		/**
 		 * Whether the driver should use encrypted traffic.
 		 */
-		private boolean encrypted = false;
+		private boolean encrypted;
 
 		/**
 		 * Trust strategy to use.

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/orm/jpa/JpaProperties.java

@@ -62,12 +62,12 @@ public class JpaProperties {
 	/**
 	 * Whether to initialize the schema on startup.
 	 */
-	private boolean generateDdl = false;
+	private boolean generateDdl;
 
 	/**
 	 * Whether to enable logging of SQL statements.
 	 */
-	private boolean showSql = false;
+	private boolean showSql;
 
 	/**
 	 * Register OpenEntityManagerInViewInterceptor. Binds a JPA EntityManager to the

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/pulsar/PulsarProperties.java

@@ -369,7 +369,7 @@ public class PulsarProperties {
 		 * Whether to throw an exception if any failure is encountered during server
 		 * shutdown while enforcing stop policy on functions.
 		 */
-		private boolean propagateStopFailures = false;
+		private boolean propagateStopFailures;
 
 		public boolean isFailFast() {
 			return this.failFast;
@@ -588,13 +588,13 @@ public class PulsarProperties {
 		/**
 		 * Priority level for shared subscription consumers.
 		 */
-		private int priorityLevel = 0;
+		private int priorityLevel;
 
 		/**
 		 * Whether to read messages from the compacted topic rather than the full message
 		 * backlog.
 		 */
-		private boolean readCompacted = false;
+		private boolean readCompacted;
 
 		/**
 		 * Dead letter policy to use.
@@ -610,7 +610,7 @@ public class PulsarProperties {
 		/**
 		 * Whether to auto retry messages.
 		 */
-		private boolean retryEnable = false;
+		private boolean retryEnable;
 
 		public String getName() {
 			return this.name;

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/quartz/QuartzProperties.java

@@ -61,12 +61,12 @@ public class QuartzProperties {
 	/**
 	 * Whether to wait for running jobs to complete on shutdown.
 	 */
-	private boolean waitForJobsToCompleteOnShutdown = false;
+	private boolean waitForJobsToCompleteOnShutdown;
 
 	/**
 	 * Whether configured jobs should overwrite existing job definitions.
 	 */
-	private boolean overwriteExistingJobs = false;
+	private boolean overwriteExistingJobs;
 
 	/**
 	 * Additional Quartz Scheduler properties.

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/r2dbc/R2dbcProperties.java

@@ -139,7 +139,7 @@ public class R2dbcProperties {
 		/**
 		 * Minimal number of idle connections.
 		 */
-		private int minIdle = 0;
+		private int minIdle;
 
 		/**
 		 * Maximum amount of time that a connection is allowed to sit idle in the pool.

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/security/oauth2/server/servlet/OAuth2AuthorizationServerProperties.java

@@ -47,7 +47,7 @@ public class OAuth2AuthorizationServerProperties implements InitializingBean {
 	 * the issuer identifier enables supporting multiple issuers per host in a
 	 * multi-tenant hosting configuration.
 	 */
-	private boolean multipleIssuersAllowed = false;
+	private boolean multipleIssuersAllowed;
 
 	/**
 	 * Registered clients of the Authorization Server.
@@ -273,12 +273,12 @@ public class OAuth2AuthorizationServerProperties implements InitializingBean {
 		 * Whether the client is required to provide a proof key challenge and verifier
 		 * when performing the Authorization Code Grant flow.
 		 */
-		private boolean requireProofKey = false;
+		private boolean requireProofKey;
 
 		/**
 		 * Whether authorization consent is required when the client requests access.
 		 */
-		private boolean requireAuthorizationConsent = false;
+		private boolean requireAuthorizationConsent;
 
 		/**
 		 * URL for the client's JSON Web Key Set.

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/sql/init/SqlInitializationProperties.java

@@ -63,7 +63,7 @@ public class SqlInitializationProperties {
 	/**
 	 * Whether initialization should continue when an error occurs.
 	 */
-	private boolean continueOnError = false;
+	private boolean continueOnError;
 
 	/**
 	 * Statement separator in the schema and data scripts.

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/template/AbstractTemplateViewResolverProperties.java

@@ -49,19 +49,19 @@ public abstract class AbstractTemplateViewResolverProperties extends AbstractVie
 	 * Whether all request attributes should be added to the model prior to merging with
 	 * the template.
 	 */
-	private boolean exposeRequestAttributes = false;
+	private boolean exposeRequestAttributes;
 
 	/**
 	 * Whether all HttpSession attributes should be added to the model prior to merging
 	 * with the template.
 	 */
-	private boolean exposeSessionAttributes = false;
+	private boolean exposeSessionAttributes;
 
 	/**
 	 * Whether HttpServletRequest attributes are allowed to override (hide) controller
 	 * generated model attributes of the same name.
 	 */
-	private boolean allowRequestOverride = false;
+	private boolean allowRequestOverride;
 
 	/**
 	 * Whether to expose a RequestContext for use by Spring's macro library, under the
@@ -73,7 +73,7 @@ public abstract class AbstractTemplateViewResolverProperties extends AbstractVie
 	 * Whether HttpSession attributes are allowed to override (hide) controller generated
 	 * model attributes of the same name.
 	 */
-	private boolean allowSessionOverride = false;
+	private boolean allowSessionOverride;
 
 	protected AbstractTemplateViewResolverProperties(String defaultPrefix, String defaultSuffix) {
 		this.prefix = defaultPrefix;

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/thymeleaf/ThymeleafProperties.java

@@ -104,7 +104,7 @@ public class ThymeleafProperties {
 	 * Whether hidden form inputs acting as markers for checkboxes should be rendered
 	 * before the checkbox element itself.
 	 */
-	private boolean renderHiddenMarkersBeforeCheckboxes = false;
+	private boolean renderHiddenMarkersBeforeCheckboxes;
 
 	/**
 	 * Whether to enable Thymeleaf view resolution for Web frameworks.

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

@@ -265,7 +265,7 @@ public class ServerProperties {
 		/**
 		 * Whether to register the default Servlet with the container.
 		 */
-		private boolean registerDefaultServlet = false;
+		private boolean registerDefaultServlet;
 
 		@NestedConfigurationProperty
 		private final Encoding encoding = new Encoding();
@@ -726,7 +726,7 @@ public class ServerProperties {
 			/**
 			 * Enable access log.
 			 */
-			private boolean enabled = false;
+			private boolean enabled;
 
 			/**
 			 * Whether logging of the request will only be enabled if
@@ -777,7 +777,7 @@ public class ServerProperties {
 			 * Whether to check for log file existence so it can be recreated if an
 			 * external process has renamed it.
 			 */
-			private boolean checkExists = false;
+			private boolean checkExists;
 
 			/**
 			 * Whether to enable access log rotation.
@@ -788,7 +788,7 @@ public class ServerProperties {
 			 * Whether to defer inclusion of the date stamp in the file name until rotate
 			 * time.
 			 */
-			private boolean renameOnRotate = false;
+			private boolean renameOnRotate;
 
 			/**
 			 * Number of days to retain the access log files before they are removed.
@@ -803,13 +803,13 @@ public class ServerProperties {
 			/**
 			 * Whether to use IPv6 canonical representation format as defined by RFC 5952.
 			 */
-			private boolean ipv6Canonical = false;
+			private boolean ipv6Canonical;
 
 			/**
 			 * Set request attributes for the IP address, Hostname, protocol, and port
 			 * used for the request.
 			 */
-			private boolean requestAttributesEnabled = false;
+			private boolean requestAttributesEnabled;
 
 			/**
 			 * Whether to buffer output such that it is flushed only periodically.
@@ -1286,7 +1286,7 @@ public class ServerProperties {
 			/**
 			 * Enable access log.
 			 */
-			private boolean enabled = false;
+			private boolean enabled;
 
 			/**
 			 * Log format.
@@ -1653,7 +1653,7 @@ public class ServerProperties {
 		 * application that requires it. Has no effect when server.undertow.decode-slash
 		 * is set.
 		 */
-		private boolean allowEncodedSlash = false;
+		private boolean allowEncodedSlash;
 
 		/**
 		 * Whether encoded slash characters (%2F) should be decoded. Decoding can cause
@@ -1689,7 +1689,7 @@ public class ServerProperties {
 		/**
 		 * Whether to preserve the path of a request when it is forwarded.
 		 */
-		private boolean preservePathOnForward = false;
+		private boolean preservePathOnForward;
 
 		private final Accesslog accesslog = new Accesslog();
 
@@ -1835,7 +1835,7 @@ public class ServerProperties {
 			/**
 			 * Whether to enable the access log.
 			 */
-			private boolean enabled = false;
+			private boolean enabled;
 
 			/**
 			 * Format pattern for access logs.

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

@@ -99,7 +99,7 @@ public class WebProperties {
 		 */
 		private boolean addMappings = true;
 
-		private boolean customized = false;
+		private boolean customized;
 
 		private final Chain chain = new Chain();
 
@@ -149,7 +149,7 @@ public class WebProperties {
 		 */
 		public static class Chain {
 
-			boolean customized = false;
+			boolean customized;
 
 			/**
 			 * Whether to enable the Spring Resource Handling chain. By default, disabled
@@ -167,7 +167,7 @@ public class WebProperties {
 			 * brotli). Checks for a resource name with the '.gz' or '.br' file
 			 * extensions.
 			 */
-			private boolean compressed = false;
+			private boolean compressed;
 
 			private final Strategy strategy = new Strategy();
 
@@ -243,7 +243,7 @@ public class WebProperties {
 				 */
 				public static class Content {
 
-					private boolean customized = false;
+					private boolean customized;
 
 					/**
 					 * Whether to enable the content Version Strategy.
@@ -284,7 +284,7 @@ public class WebProperties {
 				 */
 				public static class Fixed {
 
-					private boolean customized = false;
+					private boolean customized;
 
 					/**
 					 * Whether to enable the fixed Version Strategy.
@@ -343,7 +343,7 @@ public class WebProperties {
 		 */
 		public static class Cache {
 
-			private boolean customized = false;
+			private boolean customized;
 
 			/**
 			 * Cache period for the resources served by the resource handler. If a
@@ -395,7 +395,7 @@ public class WebProperties {
 			 */
 			public static class Cachecontrol {
 
-				private boolean customized = false;
+				private boolean customized;
 
 				/**
 				 * Maximum time the response should be cached, in seconds if no duration

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

@@ -147,7 +147,7 @@ public class WebFluxProperties {
 		/**
 		 * Whether RFC 9457 Problem Details support should be enabled.
 		 */
-		private boolean enabled = false;
+		private boolean enabled;
 
 		public boolean isEnabled() {
 			return this.enabled;

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

@@ -78,13 +78,13 @@ public class MultipartProperties {
 	 * Whether to resolve the multipart request lazily at the time of file or parameter
 	 * access.
 	 */
-	private boolean resolveLazily = false;
+	private boolean resolveLazily;
 
 	/**
 	 * Whether to resolve the multipart request strictly complying with the Servlet
 	 * specification, only to be used for "multipart/form-data" requests.
 	 */
-	private boolean strictServletCompliance = false;
+	private boolean strictServletCompliance;
 
 	public boolean getEnabled() {
 		return this.enabled;

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

@@ -49,7 +49,7 @@ public class WebMvcProperties {
 	/**
 	 * Whether to dispatch TRACE requests to the FrameworkServlet doService method.
 	 */
-	private boolean dispatchTraceRequest = false;
+	private boolean dispatchTraceRequest;
 
 	/**
 	 * Whether to dispatch OPTIONS requests to the FrameworkServlet doService method.
@@ -71,7 +71,7 @@ public class WebMvcProperties {
 	 * Whether to enable warn logging of exceptions resolved by a
 	 * "HandlerExceptionResolver", except for "DefaultHandlerExceptionResolver".
 	 */
-	private boolean logResolvedException = false;
+	private boolean logResolvedException;
 
 	/**
 	 * Path pattern used for static resources.
@@ -304,7 +304,7 @@ public class WebMvcProperties {
 		 * Whether a request parameter ("format" by default) should be used to determine
 		 * the requested media type.
 		 */
-		private boolean favorParameter = false;
+		private boolean favorParameter;
 
 		/**
 		 * Map file extensions to media types for content negotiation. For instance, yml
@@ -430,7 +430,7 @@ public class WebMvcProperties {
 		/**
 		 * Whether RFC 9457 Problem Details support should be enabled.
 		 */
-		private boolean enabled = false;
+		private boolean enabled;
 
 		public boolean isEnabled() {
 			return this.enabled;

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/batch/BatchAutoConfigurationTests.java

@@ -610,7 +610,7 @@ class BatchAutoConfigurationTests {
 		Job discreteJob() {
 			AbstractJob job = new AbstractJob("discreteRegisteredJob") {
 
-				private static int count = 0;
+				private static int count;
 
 				@Override
 				public Collection<String> getStepNames() {

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/graphql/GraphQlAutoConfigurationTests.java

@@ -323,7 +323,7 @@ class GraphQlAutoConfigurationTests {
 
 		public static class CustomRuntimeWiringConfigurer implements RuntimeWiringConfigurer {
 
-			public boolean applied = false;
+			public boolean applied;
 
 			@Override
 			public void configure(RuntimeWiring.Builder builder) {
@@ -343,7 +343,7 @@ class GraphQlAutoConfigurationTests {
 
 		public static class CustomGraphQlSourceBuilderCustomizer implements GraphQlSourceBuilderCustomizer {
 
-			public boolean applied = false;
+			public boolean applied;
 
 			@Override
 			public void customize(GraphQlSource.SchemaResourceBuilder builder) {

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/jmx/JmxAutoConfigurationTests.java

@@ -150,7 +150,7 @@ class JmxAutoConfigurationTests {
 	@ManagedResource
 	public static class Counter {
 
-		private int counter = 0;
+		private int counter;
 
 		@ManagedAttribute
 		public int get() {

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/ssl/FileWatcherTests.java

@@ -336,7 +336,7 @@ class FileWatcherTests {
 
 		private CountDownLatch latch = new CountDownLatch(1);
 
-		volatile boolean changed = false;
+		volatile boolean changed;
 
 		@Override
 		public void run() {

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/reactive/WebFluxAutoConfigurationTests.java

@@ -970,7 +970,7 @@ class WebFluxAutoConfigurationTests {
 	@Configuration(proxyBeanMethods = false)
 	static class CustomRequestMappingHandlerAdapter {
 
-		private int handlerAdapters = 0;
+		private int handlerAdapters;
 
 		@Bean
 		WebFluxRegistrations webFluxRegistrationsHandlerAdapter() {
@@ -1001,7 +1001,7 @@ class WebFluxAutoConfigurationTests {
 	@Configuration(proxyBeanMethods = false)
 	static class CustomRequestMappingHandlerMapping {
 
-		private int handlerMappings = 0;
+		private int handlerMappings;
 
 		@Bean
 		WebFluxRegistrations webFluxRegistrationsHandlerMapping() {

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/reactive/function/client/ClientHttpConnectorFactoryConfigurationTests.java

@@ -68,7 +68,7 @@ class ClientHttpConnectorFactoryConfigurationTests {
 
 	static class CustomHttpClientMapper {
 
-		static boolean called = false;
+		static boolean called;
 
 		@Bean
 		ReactorNettyHttpClientMapper clientMapper() {

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/servlet/WebMvcAutoConfigurationTests.java

@@ -1206,7 +1206,7 @@ class WebMvcAutoConfigurationTests {
 	@Configuration(proxyBeanMethods = false)
 	static class CustomRequestMappingHandlerAdapter {
 
-		private int handlerAdapters = 0;
+		private int handlerAdapters;
 
 		@Bean
 		WebMvcRegistrations webMvcRegistrationsHandlerAdapter() {
@@ -1230,7 +1230,7 @@ class WebMvcAutoConfigurationTests {
 	@Configuration(proxyBeanMethods = false)
 	static class CustomExceptionHandlerExceptionResolver {
 
-		private int exceptionResolvers = 0;
+		private int exceptionResolvers;
 
 		@Bean
 		WebMvcRegistrations webMvcRegistrationsExceptionResolver() {

spring-boot-project/spring-boot-devtools/src/test/java/org/springframework/boot/devtools/restart/RestarterTests.java

@@ -200,7 +200,7 @@ class RestarterTests {
 	@EnableScheduling
 	static class SampleApplication {
 
-		private int count = 0;
+		private int count;
 
 		private static final AtomicBoolean restart = new AtomicBoolean();
 
@@ -228,7 +228,7 @@ class RestarterTests {
 
 	static class CloseCountingApplicationListener implements ApplicationListener<ContextClosedEvent> {
 
-		static int closed = 0;
+		static int closed;
 
 		@Override
 		public void onApplicationEvent(ContextClosedEvent event) {

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

@@ -48,10 +48,10 @@ import static org.assertj.core.api.Assertions.assertThat;
 abstract class AbstractSpringBootTestEmbeddedReactiveWebEnvironmentTests {
 
 	@LocalServerPort
-	private int port = 0;
+	private int port;
 
 	@Value("${value}")
-	private int value = 0;
+	private int value;
 
 	@Autowired
 	private ReactiveWebApplicationContext context;

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

@@ -46,10 +46,10 @@ import static org.assertj.core.api.Assertions.assertThat;
 abstract class AbstractSpringBootTestWebServerWebEnvironmentTests {
 
 	@LocalServerPort
-	private int port = 0;
+	private int port;
 
 	@Value("${value}")
-	private int value = 0;
+	private int value;
 
 	@Autowired
 	private WebApplicationContext context;

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

@@ -46,7 +46,7 @@ import static org.assertj.core.api.Assertions.assertThat;
 class SpringBootTestWebEnvironmentMockTests {
 
 	@Value("${value}")
-	private int value = 0;
+	private int value;
 
 	@Autowired
 	private WebApplicationContext context;

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/mock/mockito/ResetMocksTestExecutionListenerTests.java

@@ -181,7 +181,7 @@ class ResetMocksTestExecutionListenerTests {
 
 	static class NonSingletonFactoryBean implements FactoryBean<ExampleService> {
 
-		private int getObjectInvocations = 0;
+		private int getObjectInvocations;
 
 		@Override
 		public ExampleService getObject() {

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/web/client/scan/SimpleFactoryBean.java

@@ -31,7 +31,7 @@ import org.springframework.stereotype.Component;
 @SuppressWarnings("rawtypes")
 public class SimpleFactoryBean implements FactoryBean {
 
-	private static boolean isInitializedEarly = false;
+	private static boolean isInitializedEarly;
 
 	public SimpleFactoryBean() {
 		isInitializedEarly = true;

spring-boot-project/spring-boot-testcontainers/src/dockerTest/java/org/springframework/boot/testcontainers/ImportTestcontainersTests.java

@@ -143,7 +143,7 @@ class ImportTestcontainersTests {
 	@ImportTestcontainers
 	static class NullContainer {
 
-		static PostgreSQLContainer<?> container = null;
+		static PostgreSQLContainer<?> container;
 
 	}
 

spring-boot-project/spring-boot-tools/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/docker/DockerApi.java

@@ -82,7 +82,7 @@ public class DockerApi {
 
 	private final SystemApi system;
 
-	private volatile ApiVersion apiVersion = null;
+	private volatile ApiVersion apiVersion;
 
 	/**
 	 * Create a new {@link DockerApi} instance.

spring-boot-project/spring-boot-tools/spring-boot-buildpack-platform/src/test/java/org/springframework/boot/buildpack/platform/socket/FileDescriptorTests.java

@@ -31,7 +31,7 @@ class FileDescriptorTests {
 
 	private final int sourceHandle = 123;
 
-	private int closedHandle = 0;
+	private int closedHandle;
 
 	@Test
 	void acquireReturnsHandle() throws Exception {

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/tasks/bundling/CacheSpec.java

@@ -36,7 +36,7 @@ public class CacheSpec {
 
 	private final ObjectFactory objectFactory;
 
-	private Cache cache = null;
+	private Cache cache;
 
 	@Inject
 	public CacheSpec(ObjectFactory objectFactory) {

spring-boot-project/spring-boot-tools/spring-boot-loader-classic/src/main/java/org/springframework/boot/loader/jar/JarFileEntries.java

@@ -378,7 +378,7 @@ class JarFileEntries implements CentralDirectoryVisitor, Iterable<JarEntry> {
 
 		private final Runnable validator;
 
-		private int index = 0;
+		private int index;
 
 		private EntryIterator(Runnable validator) {
 			this.validator = validator;

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

@@ -86,7 +86,7 @@ final class SizeCalculatingEntryWriter implements EntryWriter {
 	 */
 	private static class SizeCalculatingOutputStream extends OutputStream {
 
-		private int size = 0;
+		private int size;
 
 		private File tempFile;
 

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

@@ -34,7 +34,7 @@ class VirtualDataBlock implements DataBlock {
 
 	private long size;
 
-	private volatile int lastReadPart = 0;
+	private volatile int lastReadPart;
 
 	/**
 	 * Create a new {@link VirtualDataBlock} instance. The {@link #setParts(Collection)}

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

@@ -63,7 +63,7 @@ class SpringApplicationShutdownHook implements Runnable {
 
 	private final AtomicBoolean shutdownHookAdded = new AtomicBoolean();
 
-	private volatile boolean shutdownHookAdditionEnabled = false;
+	private volatile boolean shutdownHookAdditionEnabled;
 
 	private boolean inProgress;
 

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

@@ -46,7 +46,7 @@ class SpringBootExceptionHandler implements UncaughtExceptionHandler {
 
 	private final List<Throwable> loggedExceptions = new ArrayList<>();
 
-	private int exitCode = 0;
+	private int exitCode;
 
 	SpringBootExceptionHandler(UncaughtExceptionHandler parent) {
 		this.parent = parent;

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/logging/LoggingApplicationListener.java

@@ -191,7 +191,7 @@ public class LoggingApplicationListener implements GenericApplicationListener {
 
 	private boolean parseArgs = true;
 
-	private LogLevel springBootLogging = null;
+	private LogLevel springBootLogging;
 
 	@Override
 	public boolean supportsEventType(ResolvableType resolvableType) {

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

@@ -318,7 +318,7 @@ class SpringIterableConfigurationPropertySource extends SpringConfigurationPrope
 
 		private final ConfigurationPropertyName[] names;
 
-		private int index = 0;
+		private int index;
 
 		ConfigurationPropertyNamesIterator(ConfigurationPropertyName[] names) {
 			this.names = names;

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/jetty/GracefulShutdown.java

@@ -45,7 +45,7 @@ final class GracefulShutdown {
 
 	private final Supplier<Integer> activeRequests;
 
-	private volatile boolean aborted = false;
+	private volatile boolean aborted;
 
 	GracefulShutdown(Server server, Supplier<Integer> activeRequests) {
 		this.server = server;

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/tomcat/GracefulShutdown.java

@@ -44,7 +44,7 @@ final class GracefulShutdown {
 
 	private final Tomcat tomcat;
 
-	private volatile boolean aborted = false;
+	private volatile boolean aborted;
 
 	GracefulShutdown(Tomcat tomcat) {
 		this.tomcat = tomcat;

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/tomcat/NestedJarResourceSet.java

@@ -47,9 +47,9 @@ class NestedJarResourceSet extends AbstractSingleArchiveResourceSet {
 
 	private final URL url;
 
-	private JarFile archive = null;
+	private JarFile archive;
 
-	private long archiveUseCount = 0;
+	private long archiveUseCount;
 
 	private boolean useCaches;
 

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/undertow/UndertowWebServer.java

@@ -73,7 +73,7 @@ public class UndertowWebServer implements WebServer {
 
 	private Undertow undertow;
 
-	private volatile boolean started = false;
+	private volatile boolean started;
 
 	private volatile GracefulShutdownHandler gracefulShutdown;
 

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/server/Compression.java

@@ -33,7 +33,7 @@ public class Compression {
 	private String[] mimeTypes = new String[] { "text/html", "text/xml", "text/plain", "text/css", "text/javascript",
 			"application/javascript", "application/json", "application/xml" };
 
-	private String[] excludedUserAgents = null;
+	private String[] excludedUserAgents;
 
 	private DataSize minResponseSize = DataSize.ofKilobytes(2);
 

spring-boot-system-tests/spring-boot-image-tests/src/systemTest/java/org/springframework/boot/image/paketo/PaketoBuilderTests.java

@@ -565,7 +565,7 @@ class PaketoBuilderTests {
 
 	private static class DigestCapturingCondition extends Condition<Object> {
 
-		private static String digest = null;
+		private static String digest;
 
 		DigestCapturingCondition() {
 			super(predicate(), "a value starting with 'sha256:'");

spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-websocket-jetty/src/main/java/smoketest/websocket/jetty/snake/SnakeTimer.java

@@ -40,7 +40,7 @@ public final class SnakeTimer {
 
 	private static final ConcurrentHashMap<Integer, Snake> snakes = new ConcurrentHashMap<>();
 
-	private static Timer gameTimer = null;
+	private static Timer gameTimer;
 
 	private SnakeTimer() {
 	}

spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-websocket-tomcat/src/main/java/smoketest/websocket/tomcat/snake/SnakeTimer.java

@@ -40,7 +40,7 @@ public final class SnakeTimer {
 
 	private static final ConcurrentHashMap<Integer, Snake> snakes = new ConcurrentHashMap<>();
 
-	private static Timer gameTimer = null;
+	private static Timer gameTimer;
 
 	private SnakeTimer() {
 	}

spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-websocket-undertow/src/main/java/smoketest/websocket/undertow/snake/SnakeTimer.java

@@ -40,7 +40,7 @@ public final class SnakeTimer {
 
 	private static final ConcurrentHashMap<Integer, Snake> snakes = new ConcurrentHashMap<>();
 
-	private static Timer gameTimer = null;
+	private static Timer gameTimer;
 
 	private SnakeTimer() {
 	}

src/checkstyle/checkstyle.xml

@@ -13,6 +13,7 @@
 	<module name="com.puppycrawl.tools.checkstyle.TreeWalker">
 		<module name="io.spring.javaformat.checkstyle.check.SpringDeprecatedCheck" />
 		<module name="io.spring.javaformat.checkstyle.check.SpringJUnit5Check" />
+		<module name="ExplicitInitialization" />
 		<module
 			name="com.puppycrawl.tools.checkstyle.checks.imports.IllegalImportCheck">
 			<property name="regexp" value="true" />