Remove unnecessary field initialization

Closes gh-45168

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

Author: snicoll

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

@@ -142,7 +142,7 @@ public Iterator<Node> iterator() {
 
 			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 static class Brave {
 		 * 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 @@ public static class TestProperties {
 
 		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 static class DirectContainer extends AmqpContainer {
 		 * 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 @@
  */
 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 static class Pool {
 		 * 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