Add `@Contract` and `@CheckReturnValue` annotations.

src/main/java/org/springframework/data/annotation/AccessType.java

@@ -34,8 +34,6 @@ public @interface AccessType {
 
 	/**
 	 * The access type to be used.
-	 *
-	 * @return
 	 */
 	Type value();
 

src/main/java/org/springframework/data/annotation/PersistenceCreator.java

@@ -29,4 +29,5 @@ import java.lang.annotation.Target;
  */
 @Retention(RetentionPolicy.RUNTIME)
 @Target({ ElementType.CONSTRUCTOR, ElementType.METHOD, ElementType.ANNOTATION_TYPE })
-public @interface PersistenceCreator {}
+public @interface PersistenceCreator {
+}

src/main/java/org/springframework/data/annotation/Reference.java

@@ -36,8 +36,6 @@ public @interface Reference {
 	/**
 	 * Explicitly define the target type of the reference. Used in case the annotated property is not the target type but
 	 * rather an identifier and/or if that identifier type is not uniquely identifying the target entity.
-	 *
-	 * @return
 	 */
 	@AliasFor(attribute = "to")
 	Class<?> value() default Class.class;
@@ -45,8 +43,6 @@ public @interface Reference {
 	/**
 	 * Explicitly define the target type of the reference. Used in case the annotated property is not the target type but
 	 * rather an identifier and/or if that identifier type is not uniquely identifying the target entity.
-	 *
-	 * @return
 	 */
 	@AliasFor(attribute = "value")
 	Class<?> to() default Class.class;

src/main/java/org/springframework/data/annotation/TypeAlias.java

@@ -29,6 +29,7 @@ import org.springframework.data.mapping.PersistentEntity;
  * {@link PersistentEntity}s.
  *
  * @author Oliver Gierke
+ * @see org.springframework.data.mapping.Alias
  */
 @Documented
 @Inherited
@@ -38,9 +39,7 @@ import org.springframework.data.mapping.PersistentEntity;
 public @interface TypeAlias {
 
 	/**
-	 * The type alias to be used when persisting
-	 *
-	 * @return
+	 * The type alias to be used when persisting.
 	 */
 	String value();
 }

src/main/java/org/springframework/data/annotation/Version.java

@@ -33,5 +33,4 @@ import java.lang.annotation.Target;
 @Retention(RUNTIME)
 @Target(value = { FIELD, METHOD, ANNOTATION_TYPE })
 public @interface Version {
-
 }

src/main/java/org/springframework/data/aot/AotContext.java

@@ -140,7 +140,7 @@ public interface AotContext {
 	}
 
 	/**
-	 * Returns a {@link IntrospectedBeanDefinition} to obtain further detail about the underlying bean definition. A
+	 * Returns a {@link IntrospectedBeanDefinition} to obtain further detail about the underlying bean definition. An
 	 * introspected bean definition can also point to an absent bean definition.
 	 *
 	 * @param reference {@link BeanReference} to the managed bean.
@@ -151,7 +151,7 @@ public interface AotContext {
 	}
 
 	/**
-	 * Returns a {@link IntrospectedBeanDefinition} to obtain further detail about the underlying bean definition. A
+	 * Returns a {@link IntrospectedBeanDefinition} to obtain further detail about the underlying bean definition. An
 	 * introspected bean definition can also point to an absent bean definition.
 	 *
 	 * @param beanName {@link String} containing the {@literal name} of the bean to evaluate; must not be {@literal null}.
@@ -251,7 +251,6 @@ public interface AotContext {
 		 *           bean}.
 		 * @see BeanDefinition
 		 */
-
 		BeanDefinition getBeanDefinition() throws NoSuchBeanDefinitionException;
 
 		/**

src/main/java/org/springframework/data/aot/AuditingBeanRegistrationAotProcessor.java

@@ -39,7 +39,6 @@ import org.springframework.util.ClassUtils;
  */
 class AuditingBeanRegistrationAotProcessor implements BeanRegistrationAotProcessor {
 
-
 	@Nullable
 	@Override
 	public BeanRegistrationAotContribution processAheadOfTime(RegisteredBean registeredBean) {

src/main/java/org/springframework/data/aot/ManagedTypesBeanFactoryInitializationAotProcessor.java

@@ -29,6 +29,7 @@ import org.springframework.beans.factory.config.ConstructorArgumentValues.ValueH
 import org.springframework.beans.factory.support.BeanDefinitionBuilder;
 import org.springframework.beans.factory.support.BeanDefinitionRegistry;
 import org.springframework.data.domain.ManagedTypes;
+import org.springframework.lang.Contract;
 import org.springframework.lang.Nullable;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.ObjectUtils;
@@ -44,10 +45,11 @@ import org.springframework.util.ObjectUtils;
  */
 public class ManagedTypesBeanFactoryInitializationAotProcessor implements BeanFactoryInitializationAotProcessor {
 
-	private static final Log logger = LogFactory.getLog(BeanFactoryInitializationAotProcessor.class);
+	private static final Log logger = LogFactory.getLog(ManagedTypesBeanFactoryInitializationAotProcessor.class);
 
-	@Nullable
 	@Override
+	@Nullable
+	@Contract("_ -> null")
 	public BeanFactoryInitializationAotContribution processAheadOfTime(ConfigurableListableBeanFactory beanFactory) {
 
 		processManagedTypes(beanFactory);
@@ -71,9 +73,9 @@ public class ManagedTypesBeanFactoryInitializationAotProcessor implements BeanFa
 
 		if (hasConstructorArguments(beanDefinition)) {
 
-			ValueHolder argumentValue = beanDefinition.getConstructorArgumentValues().getArgumentValue(0, null, null, null);
+			ValueHolder holder = beanDefinition.getConstructorArgumentValues().getArgumentValue(0, null, null, null);
 
-			if (argumentValue.getValue()instanceof Supplier supplier) {
+			if (holder != null && holder.getValue() instanceof Supplier<?> supplier) {
 
 				if (logger.isDebugEnabled()) {
 					logger.info(String.format("Replacing ManagedType bean definition %s.", beanName));

src/main/java/org/springframework/data/aot/ManagedTypesBeanRegistrationAotProcessor.java

@@ -78,9 +78,9 @@ public class ManagedTypesBeanRegistrationAotProcessor implements BeanRegistratio
 		if (beanDefinition.hasConstructorArgumentValues()) {
 
 			ValueHolder indexedArgumentValue = beanDefinition.getConstructorArgumentValues().getIndexedArgumentValue(0, null);
-			Object value = indexedArgumentValue.getValue();
 
-			if (value instanceof Collection<?> values && values.stream().allMatch(it -> it instanceof Class)) {
+			if (indexedArgumentValue != null && indexedArgumentValue.getValue() instanceof Collection<?> values
+					&& values.stream().allMatch(it -> it instanceof Class)) {
 				return ManagedTypes.fromIterable((Collection<Class<?>>) values);
 			}
 		}
@@ -115,7 +115,6 @@ public class ManagedTypesBeanRegistrationAotProcessor implements BeanRegistratio
 	 * @param managedTypes never {@literal null}.
 	 * @return new instance of {@link BeanRegistrationAotContribution} or {@literal null} if nothing to do.
 	 */
-	@Nullable
 	protected BeanRegistrationAotContribution contribute(AotContext aotContext, ManagedTypes managedTypes,
 			RegisteredBean registeredBean) {
 		return new ManagedTypesRegistrationAotContribution(managedTypes, registeredBean, this::contributeType);

src/main/java/org/springframework/data/aot/ManagedTypesRegistrationAotContribution.java

@@ -15,7 +15,6 @@
  */
 package org.springframework.data.aot;
 
-import java.lang.reflect.Executable;
 import java.lang.reflect.Method;
 import java.util.Collections;
 import java.util.List;
@@ -69,8 +68,8 @@ import org.springframework.util.ReflectionUtils;
  * @author John Blum
  * @author Christoph Strobl
  * @author Mark Paluch
- * @see org.springframework.beans.factory.aot.BeanRegistrationAotContribution
  * @since 3.0
+ * @see org.springframework.beans.factory.aot.BeanRegistrationAotContribution
  */
 class ManagedTypesRegistrationAotContribution implements RegisteredBeanAotContribution {
 
@@ -126,7 +125,7 @@ class ManagedTypesRegistrationAotContribution implements RegisteredBeanAotContri
 		public static final ResolvableType MANAGED_TYPES_TYPE = ResolvableType.forType(ManagedTypes.class);
 		private final List<Class<?>> sourceTypes;
 		private final RegisteredBean source;
-		private final Lazy<Method> instanceMethod = Lazy.of(this::findInstanceFactory);
+		private final Lazy<Method> instanceMethod;
 
 		private static final TypeName WILDCARD = WildcardTypeName.subtypeOf(Object.class);
 		private static final TypeName CLASS_OF_ANY = ParameterizedTypeName.get(ClassName.get(Class.class), WILDCARD);
@@ -139,6 +138,7 @@ class ManagedTypesRegistrationAotContribution implements RegisteredBeanAotContri
 
 			this.sourceTypes = sourceTypes;
 			this.source = source;
+			this.instanceMethod = Lazy.of(() -> findInstanceFactory(source.getBeanClass()));
 		}
 
 		@Override
@@ -230,15 +230,15 @@ class ManagedTypesRegistrationAotContribution implements RegisteredBeanAotContri
 		}
 
 		@Nullable
-		private Method findInstanceFactory() {
+		private static Method findInstanceFactory(Class<?> beanClass) {
 
-			for (Method beanMethod : ReflectionUtils.getDeclaredMethods(source.getBeanClass())) {
+			for (Method beanMethod : ReflectionUtils.getDeclaredMethods(beanClass)) {
 
 				if (!isInstanceFactory(beanMethod)) {
 					continue;
 				}
 
-				ResolvableType parameterType = ResolvableType.forMethodParameter(beanMethod, 0, source.getBeanClass());
+				ResolvableType parameterType = ResolvableType.forMethodParameter(beanMethod, 0, beanClass);
 
 				if (parameterType.isAssignableFrom(LIST_TYPE) || parameterType.isAssignableFrom(MANAGED_TYPES_TYPE)) {
 					return beanMethod;

src/main/java/org/springframework/data/aot/PublicMethodReflectiveProcessor.java

@@ -20,6 +20,8 @@ import org.springframework.aot.hint.ReflectionHints;
 import org.springframework.aot.hint.annotation.SimpleReflectiveProcessor;
 
 /**
+ * Extension to {@link SimpleReflectiveProcessor} to register reflective hints for invoking public methods.
+ *
  * @author Christoph Strobl
  */
 public class PublicMethodReflectiveProcessor extends SimpleReflectiveProcessor {

src/main/java/org/springframework/data/aot/RegisteredBeanAotContribution.java

@@ -19,7 +19,7 @@ import org.springframework.beans.factory.aot.BeanRegistrationAotContribution;
 import org.springframework.beans.factory.support.RegisteredBean;
 
 /**
- * Extension to {@link BeanRegistrationAotContribution} that bases its contribution on a {@link RegisteredBean}. This
+ * Extension to {@link BeanRegistrationAotContribution} that bases its contribution to a {@link RegisteredBean}. This
  * interface exposes its {@link #getSource() source}.
  *
  * @author Christoph Strobl

src/main/java/org/springframework/data/auditing/AuditableBeanWrapper.java

@@ -18,6 +18,9 @@ package org.springframework.data.auditing;
 import java.time.temporal.TemporalAccessor;
 import java.util.Optional;
 
+import org.springframework.lang.Contract;
+import org.springframework.lang.Nullable;
+
 /**
  * Interface to abstract the ways setting the auditing information can be implemented.
  *
@@ -31,7 +34,9 @@ public interface AuditableBeanWrapper<T> {
 	 *
 	 * @param value
 	 */
-	Object setCreatedBy(Object value);
+	@Nullable
+	@Contract("null -> null; !null -> !null")
+	Object setCreatedBy(@Nullable Object value);
 
 	/**
 	 * Set the date the object was created.
@@ -45,7 +50,9 @@ public interface AuditableBeanWrapper<T> {
 	 *
 	 * @param value
 	 */
-	Object setLastModifiedBy(Object value);
+	@Nullable
+	@Contract("null -> null; !null -> !null")
+	Object setLastModifiedBy(@Nullable Object value);
 
 	/**
 	 * Returns the date of the last modification date of the backing bean.

src/main/java/org/springframework/data/auditing/AuditingHandler.java

@@ -104,9 +104,10 @@ public class AuditingHandler extends AuditingHandlerSupport implements Initializ
 				.orElse(Auditor.none());
 	}
 
+	@Override
 	public void afterPropertiesSet() {
 
-		if (!auditorAware.isPresent()) {
+		if (auditorAware.isEmpty()) {
 			logger.debug("No AuditorAware set; Auditing will not be applied");
 		}
 	}

src/main/java/org/springframework/data/auditing/AuditingHandlerSupport.java

@@ -151,11 +151,6 @@ public abstract class AuditingHandlerSupport {
 
 	/**
 	 * Sets modifying and creating auditor. Creating auditor is only set on new auditables.
-	 *
-	 * @param auditor
-	 * @param wrapper
-	 * @param isNew
-	 * @return
 	 */
 	private void touchAuditor(Auditor<?> auditor, AuditableBeanWrapper<?> wrapper, boolean isNew) {
 
@@ -176,10 +171,6 @@ public abstract class AuditingHandlerSupport {
 
 	/**
 	 * Touches the auditable regarding modification and creation date. Creation date is only set on new auditables.
-	 *
-	 * @param wrapper
-	 * @param isNew
-	 * @return
 	 */
 	private Optional<TemporalAccessor> touchDate(AuditableBeanWrapper<?> wrapper, boolean isNew) {
 

src/main/java/org/springframework/data/auditing/Auditor.java

@@ -28,7 +28,7 @@ import org.springframework.util.ObjectUtils;
  */
 class Auditor<T> {
 
-	private static final Auditor NONE = new Auditor(null) {
+	private static final Auditor<Object> NONE = new Auditor<>(null) {
 
 		@Override
 		public boolean isPresent() {
@@ -59,6 +59,7 @@ class Auditor<T> {
 	 * @param <T>
 	 * @return {@link Auditor#none()} if the given {@literal source} is {@literal null}. }
 	 */
+	@SuppressWarnings({ "unchecked", "rawtypes" })
 	public static <T> Auditor<T> of(@Nullable T source) {
 
 		if (source instanceof Auditor) {
@@ -77,7 +78,7 @@ class Auditor<T> {
 	 * @param <T>
 	 * @return {@link Auditor#none()} if the given {@literal source} is {@literal null}. }
 	 */
-	public static <T> Auditor<T> ofOptional(@Nullable Optional<T> source) {
+	public static <T> Auditor<T> ofOptional(Optional<T> source) {
 		return Auditor.of(source.orElse(null));
 	}
 
@@ -87,8 +88,9 @@ class Auditor<T> {
 	 * @param <T>
 	 * @return never {@literal null}.
 	 */
+	@SuppressWarnings("unchecked")
 	public static <T> Auditor<T> none() {
-		return NONE;
+		return (Auditor<T>) NONE;
 	}
 
 	/**

src/main/java/org/springframework/data/auditing/DefaultAuditableBeanWrapperFactory.java

@@ -115,7 +115,7 @@ class DefaultAuditableBeanWrapperFactory implements AuditableBeanWrapperFactory
 		}
 
 		@Override
-		public Object setCreatedBy(Object value) {
+		public Object setCreatedBy(@Nullable Object value) {
 
 			auditable.setCreatedBy(value);
 			return value;
@@ -267,7 +267,7 @@ class DefaultAuditableBeanWrapperFactory implements AuditableBeanWrapperFactory
 		}
 
 		@Override
-		public Object setCreatedBy(Object value) {
+		public Object setCreatedBy(@Nullable Object value) {
 			return setField(metadata.getCreatedByField(), value);
 		}
 
@@ -277,7 +277,7 @@ class DefaultAuditableBeanWrapperFactory implements AuditableBeanWrapperFactory
 		}
 
 		@Override
-		public Object setLastModifiedBy(Object value) {
+		public Object setLastModifiedBy(@Nullable Object value) {
 			return setField(metadata.getLastModifiedByField(), value);
 		}
 
@@ -308,7 +308,8 @@ class DefaultAuditableBeanWrapperFactory implements AuditableBeanWrapperFactory
 		 * @param field
 		 * @param value
 		 */
-		private <S> S setField(Optional<Field> field, S value) {
+		@Nullable
+		private <S> S setField(Optional<Field> field, @Nullable S value) {
 
 			field.ifPresent(it -> ReflectionUtils.setField(it, target, value));
 

src/main/java/org/springframework/data/auditing/MappingAuditableBeanWrapperFactory.java

@@ -40,6 +40,8 @@ import org.springframework.data.mapping.PersistentPropertyPaths;
 import org.springframework.data.mapping.context.MappingContext;
 import org.springframework.data.mapping.context.PersistentEntities;
 import org.springframework.data.util.Lazy;
+import org.springframework.lang.Contract;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -203,7 +205,7 @@ public class MappingAuditableBeanWrapperFactory extends DefaultAuditableBeanWrap
 		}
 
 		@Override
-		public Object setLastModifiedBy(Object value) {
+		public Object setLastModifiedBy(@Nullable Object value) {
 			return setProperty(metadata.lastModifiedByPaths, value);
 		}
 
@@ -226,8 +228,10 @@ public class MappingAuditableBeanWrapperFactory extends DefaultAuditableBeanWrap
 			return accessor.getBean();
 		}
 
+		@Nullable
+		@Contract("_, null -> null; _, !null -> !null")
 		private <S> S setProperty(
-				PersistentPropertyPaths<?, ? extends PersistentProperty<?>> paths, S value) {
+				PersistentPropertyPaths<?, ? extends PersistentProperty<?>> paths, @Nullable S value) {
 
 			paths.forEach(it -> this.accessor.setProperty(it, value, OPTIONS));
 

src/main/java/org/springframework/data/auditing/config/AuditingBeanDefinitionRegistrarSupport.java

@@ -65,7 +65,7 @@ public abstract class AuditingBeanDefinitionRegistrarSupport implements ImportBe
 	 *
 	 * @param configuration must not be {@literal null}.
 	 * @param registry must not be {@literal null}.
-	 * @return
+	 * @return the {@link AbstractBeanDefinition} for the {@link AuditingConfiguration}.
 	 */
 	protected AbstractBeanDefinition registerAuditHandlerBeanDefinition(AuditingConfiguration configuration,
 			BeanDefinitionRegistry registry) {
@@ -96,7 +96,7 @@ public abstract class AuditingBeanDefinitionRegistrarSupport implements ImportBe
 	 * implementations.
 	 *
 	 * @param configuration must not be {@literal null}.
-	 * @return
+	 * @return the {@link BeanDefinitionBuilder} for the {@link AuditingConfiguration}.
 	 */
 	protected BeanDefinitionBuilder getAuditHandlerBeanDefinitionBuilder(AuditingConfiguration configuration) {
 
@@ -142,7 +142,7 @@ public abstract class AuditingBeanDefinitionRegistrarSupport implements ImportBe
 	 * Retrieve auditing configuration from the given {@link AnnotationMetadata}.
 	 *
 	 * @param annotationMetadata will never be {@literal null}.
-	 * @return
+	 * @return a new {@link AnnotationAuditingConfiguration}.
 	 */
 	protected AuditingConfiguration getConfiguration(AnnotationMetadata annotationMetadata) {
 		return new AnnotationAuditingConfiguration(annotationMetadata, getAnnotation());
@@ -167,7 +167,7 @@ public abstract class AuditingBeanDefinitionRegistrarSupport implements ImportBe
 	/**
 	 * Return the name to be used to register the {@link AuditingHandler} under.
 	 *
-	 * @return
+	 * @return name of the {@link AuditingHandler} bean.
 	 */
 	protected abstract String getAuditingHandlerBeanName();
 

src/main/java/org/springframework/data/auditing/config/AuditingHandlerBeanDefinitionParser.java

@@ -29,9 +29,9 @@ import org.springframework.data.auditing.AuditingHandler;
 import org.springframework.data.config.ParsingUtils;
 import org.springframework.data.mapping.context.MappingContext;
 import org.springframework.data.repository.config.PersistentEntitiesFactoryBean;
-import org.springframework.lang.NonNull;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
+
 import org.w3c.dom.Element;
 
 /**
@@ -69,7 +69,6 @@ public class AuditingHandlerBeanDefinitionParser extends AbstractSingleBeanDefin
 		return resolvedBeanName;
 	}
 
-	@NonNull
 	@Override
 	protected Class<?> getBeanClass(Element element) {
 		return AuditingHandler.class;

src/main/java/org/springframework/data/config/ConfigurationUtils.java

@@ -38,7 +38,7 @@ public interface ConfigurationUtils {
 	 * @return
 	 * @throws IllegalArgumentException if no {@link ResourceLoader} can be obtained from the {@link XmlReaderContext}.
 	 */
-	public static ResourceLoader getRequiredResourceLoader(XmlReaderContext context) {
+	static ResourceLoader getRequiredResourceLoader(XmlReaderContext context) {
 
 		Assert.notNull(context, "XmlReaderContext must not be null");
 
@@ -58,7 +58,7 @@ public interface ConfigurationUtils {
 	 * @return
 	 * @throws IllegalArgumentException if no {@link ClassLoader} can be obtained from the given {@link XmlReaderContext}.
 	 */
-	public static ClassLoader getRequiredClassLoader(XmlReaderContext context) {
+	static ClassLoader getRequiredClassLoader(XmlReaderContext context) {
 		return getRequiredClassLoader(getRequiredResourceLoader(context));
 	}
 
@@ -69,7 +69,7 @@ public interface ConfigurationUtils {
 	 * @return
 	 * @throws IllegalArgumentException if the given {@link ResourceLoader} does not expose a {@link ClassLoader}.
 	 */
-	public static ClassLoader getRequiredClassLoader(ResourceLoader resourceLoader) {
+	static ClassLoader getRequiredClassLoader(ResourceLoader resourceLoader) {
 
 		Assert.notNull(resourceLoader, "ResourceLoader must not be null");
 
@@ -89,7 +89,7 @@ public interface ConfigurationUtils {
 	 * @return
 	 * @throws IllegalArgumentException if the given {@link BeanDefinition} does not contain a bean class name.
 	 */
-	public static String getRequiredBeanClassName(BeanDefinition beanDefinition) {
+	static String getRequiredBeanClassName(BeanDefinition beanDefinition) {
 
 		Assert.notNull(beanDefinition, "BeanDefinition must not be null");
 

src/main/java/org/springframework/data/convert/AnnotatedPropertyValueConverterAccessor.java

@@ -27,12 +27,15 @@ import org.springframework.util.Assert;
  */
 class AnnotatedPropertyValueConverterAccessor {
 
+	private final String name;
 	private final ValueConverter annotation;
 
 	public AnnotatedPropertyValueConverterAccessor(PersistentProperty<?> property) {
 
 		Assert.notNull(property, "PersistentProperty must not be null");
-		annotation = property.findAnnotation(ValueConverter.class);
+
+		this.name = property.toString();
+		this.annotation = property.findAnnotation(ValueConverter.class);
 	}
 
 	/**
@@ -48,6 +51,28 @@ class AnnotatedPropertyValueConverterAccessor {
 		return annotation != null ? (Class) annotation.value() : null;
 	}
 
+	/**
+	 * Obtain the required {@link PropertyValueConverter converter type} to be used for reading and writing property
+	 * values. Uses the {@link ValueConverter} annotation and extracts its {@link ValueConverter#value() value} attribute.
+	 * Throws {@link IllegalStateException} if no converter is defined.
+	 *
+	 * @return {@literal null} if none defined. Check {@link #hasValueConverter()} to check if the annotation is present
+	 *         at all.
+	 * @since 4.0
+	 * @throws IllegalStateException if no converter is defined.
+	 */
+	public Class<? extends PropertyValueConverter<?, ?, ? extends ValueConversionContext<? extends PersistentProperty<?>>>> getRequiredValueConverterType()
+			throws IllegalStateException {
+
+		Class<? extends PropertyValueConverter<?, ?, ? extends ValueConversionContext<? extends PersistentProperty<?>>>> converterType = getValueConverterType();
+
+		if (converterType == null) {
+			throw new IllegalStateException("No converter defined for property '" + name + "'");
+		}
+
+		return converterType;
+	}
+
 	/**
 	 * Return whether a value converter is configured. Uses {@link ValueConverter} as annotation type.
 	 *

src/main/java/org/springframework/data/convert/CustomConversions.java

@@ -198,10 +198,6 @@ public class CustomConversions {
 	 * @param type {@link Class} to evaluate as a simple type, such as a primitive type.
 	 * @return a boolean value indicating whether the given, required {@link Class type} is simple.
 	 */
-	// TODO: Technically, an 'isXyz(..)' method (returning a boolean to answer a user's question should not throw an
-	// Exception).
-	// Rather, a null Class type argument should simply return false to indicate it is clearly not a "simple type".
-	// How much data store specific code relies on the existing behavior?
 	public boolean isSimpleType(Class<?> type) {
 
 		Assert.notNull(type, "Type must not be null");
@@ -229,6 +225,7 @@ public class CustomConversions {
 	 * @param candidate must not be {@literal null}.
 	 * @param conversionService must not be {@literal null}.
 	 */
+	@SuppressWarnings("rawtypes")
 	private void registerConverterIn(Object candidate, ConverterRegistry conversionService) {
 
 		if (candidate instanceof Converter converter) {
@@ -669,7 +666,7 @@ public class CustomConversions {
 			return isConverterOfSource(ConverterOrigin.DEFAULT);
 		}
 
-		public ConverterRegistration getConverterRegistration() {
+		ConverterRegistration getConverterRegistration() {
 			return delegate;
 		}
 
@@ -815,7 +812,7 @@ public class CustomConversions {
 		 * @param converter must not be {@literal null}.
 		 * @return
 		 */
-		public Streamable<ConverterRegistration> getRegistrationsFor(Object converter) {
+		Streamable<ConverterRegistration> getRegistrationsFor(Object converter) {
 
 			Assert.notNull(converter, "Converter must not be null");
 

src/main/java/org/springframework/data/convert/DefaultTypeMapper.java

@@ -141,8 +141,8 @@ public class DefaultTypeMapper<S> implements TypeMapper<S>, BeanClassLoaderAware
 
 		Class<T> rawType = basicType.getType();
 
-		boolean isMoreConcreteCustomType = (rawType == null)
-				|| (rawType.isAssignableFrom(documentsTargetType) && !rawType.equals(documentsTargetType));
+		boolean isMoreConcreteCustomType = (rawType.isAssignableFrom(documentsTargetType)
+				&& !rawType.equals(documentsTargetType));
 
 		if (!isMoreConcreteCustomType) {
 			return basicType;
@@ -163,10 +163,9 @@ public class DefaultTypeMapper<S> implements TypeMapper<S>, BeanClassLoaderAware
 	@Nullable
 	private Class<?> getDefaultedTypeToBeUsed(S source) {
 
-		TypeInformation<?> documentsTargetTypeInformation = readType(source);
-		documentsTargetTypeInformation = documentsTargetTypeInformation == null ? getFallbackTypeFor(source)
-				: documentsTargetTypeInformation;
-		return documentsTargetTypeInformation == null ? null : documentsTargetTypeInformation.getType();
+		TypeInformation<?> type = readType(source);
+		type = type == null ? getFallbackTypeFor(source) : type;
+		return type == null ? null : type.getType();
 	}
 
 	/**
@@ -192,7 +191,7 @@ public class DefaultTypeMapper<S> implements TypeMapper<S>, BeanClassLoaderAware
 
 		Alias alias = getAliasFor(info);
 		if (alias.isPresent()) {
-			accessor.writeTypeTo(sink, alias.getValue());
+			accessor.writeTypeTo(sink, alias.getRequiredValue());
 		}
 	}
 

src/main/java/org/springframework/data/convert/DtoInstantiatingConverter.java

@@ -27,7 +27,7 @@ import org.springframework.data.mapping.context.MappingContext;
 import org.springframework.data.mapping.model.EntityInstantiator;
 import org.springframework.data.mapping.model.EntityInstantiators;
 import org.springframework.data.mapping.model.ParameterValueProvider;
-import org.springframework.lang.NonNull;
+import org.springframework.lang.Contract;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
@@ -64,8 +64,8 @@ public class DtoInstantiatingConverter implements Converter<Object, Object> {
 		this.instantiator = instantiators.getInstantiatorFor(context.getRequiredPersistentEntity(dtoType));
 	}
 
-	@NonNull
 	@Override
+	@Contract("_ -> !null")
 	public Object convert(Object source) {
 
 		if (targetType.isInterface()) {
@@ -82,6 +82,7 @@ public class DtoInstantiatingConverter implements Converter<Object, Object> {
 
 			@Override
 			@Nullable
+			@SuppressWarnings({ "rawtypes" })
 			public Object getParameterValue(Parameter parameter) {
 
 				String name = parameter.getName();

src/main/java/org/springframework/data/convert/EntityReader.java

@@ -27,7 +27,7 @@ public interface EntityReader<T, S> {
 	 *
 	 * @param type they type to convert the given source to.
 	 * @param source the source to create an object of the given type from.
-	 * @return
+	 * @return the converted object.
 	 */
 	<R extends T> R read(Class<R> type, S source);
 }

src/main/java/org/springframework/data/convert/EntityWriter.java

@@ -24,5 +24,11 @@ package org.springframework.data.convert;
  */
 public interface EntityWriter<T, S> {
 
+	/**
+	 * Writes the given source object into a store specific sink.
+	 *
+	 * @param source the source to create an object of the given type from.
+	 * @param sink the sink to write into.
+	 */
 	void write(T source, S sink);
 }

src/main/java/org/springframework/data/convert/JMoleculesConverters.java

@@ -54,8 +54,7 @@ public class JMoleculesConverters {
 
 		List<Object> converters = new ArrayList<>();
 
-		Supplier<ConversionService> conversionService = (Supplier<ConversionService>) () -> DefaultConversionService
-				.getSharedInstance();
+		Supplier<ConversionService> conversionService = DefaultConversionService::getSharedInstance;
 
 		IdentifierToPrimitivesConverter toPrimitives = new IdentifierToPrimitivesConverter(conversionService);
 		PrimitivesToIdentifierConverter toIdentifier = new PrimitivesToIdentifierConverter(conversionService);

src/main/java/org/springframework/data/convert/MappingContextTypeInformationMapper.java

@@ -65,7 +65,7 @@ public class MappingContextTypeInformationMapper implements TypeInformationMappe
 
 			PersistentEntity<?, ? extends PersistentProperty<?>> entity = mappingContext.getPersistentEntity(key);
 
-			if (entity == null || entity.getTypeAlias() == null) {
+			if (entity == null || entity.getTypeAlias().isEmpty()) {
 				return Alias.NONE;
 			}
 

src/main/java/org/springframework/data/convert/PropertyValueConverterFactories.java

@@ -27,6 +27,7 @@ import org.springframework.beans.BeanUtils;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.config.AutowireCapableBeanFactory;
 import org.springframework.data.mapping.PersistentProperty;
+import org.springframework.lang.Contract;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
@@ -175,6 +176,7 @@ final class PropertyValueConverterFactories {
 	 * @author Christoph Strobl
 	 * @since 2.7
 	 */
+	@SuppressWarnings("OptionalAssignedToNull")
 	static class CachingPropertyValueConverterFactory implements PropertyValueConverterFactory {
 
 		private final PropertyValueConverterFactory delegate;
@@ -225,6 +227,8 @@ final class PropertyValueConverterFactories {
 				return typeCache.get(type);
 			}
 
+			@Nullable
+			@Contract("_, null -> null;_, !null -> !null")
 			<S, T, C extends ValueConversionContext<?>> PropertyValueConverter<S, T, C> cache(PersistentProperty<?> property,
 					@Nullable PropertyValueConverter<S, T, C> converter) {
 
@@ -241,6 +245,8 @@ final class PropertyValueConverterFactories {
 				return converter;
 			}
 
+			@Nullable
+			@Contract("_, null -> null;_, !null -> !null")
 			<S, T, C extends ValueConversionContext<?>> PropertyValueConverter<S, T, C> cache(Class<?> type,
 					@Nullable PropertyValueConverter<S, T, C> converter) {
 

src/main/java/org/springframework/data/convert/PropertyValueConverterFactory.java

@@ -60,7 +60,7 @@ public interface PropertyValueConverterFactory {
 			return null;
 		}
 
-		return getConverter((Class<PropertyValueConverter<DV, SV, P>>) accessor.getValueConverterType());
+		return getConverter((Class<PropertyValueConverter<DV, SV, P>>) accessor.getRequiredValueConverterType());
 	}
 
 	/**

src/main/java/org/springframework/data/convert/PropertyValueConverterRegistrar.java

@@ -22,6 +22,7 @@ import java.util.function.Function;
 import org.springframework.data.convert.PropertyValueConverter.FunctionPropertyValueConverter;
 import org.springframework.data.mapping.PersistentProperty;
 import org.springframework.data.util.MethodInvocationRecorder;
+import org.springframework.lang.Contract;
 import org.springframework.util.Assert;
 
 /**
@@ -87,6 +88,7 @@ public class PropertyValueConverterRegistrar<P extends PersistentProperty<P>> {
 	 * @param converter the {@link PropertyValueConverter converter} to apply.
 	 * @return this.
 	 */
+	@Contract("_, _, _ -> this")
 	public PropertyValueConverterRegistrar<P> registerConverter(Class<?> type, String path,
 			PropertyValueConverter<?, ?, ? extends ValueConversionContext<?>> converter) {
 

src/main/java/org/springframework/data/convert/SimplePropertyValueConverterRegistry.java

@@ -67,6 +67,7 @@ public class SimplePropertyValueConverterRegistry<P extends PersistentProperty<P
 	}
 
 	@Override
+	@SuppressWarnings("unchecked")
 	public <S, T> PropertyValueConverter<S, T, ? extends ValueConversionContext<P>> getConverter(Class<?> type,
 			String path) {
 

src/main/java/org/springframework/data/crossstore/ChangeSetBackedTransactionSynchronization.java

@@ -35,12 +35,14 @@ public class ChangeSetBackedTransactionSynchronization implements TransactionSyn
 		this.entity = entity;
 	}
 
+	@Override
 	public void afterCommit() {
 		logger.debug("After Commit called for " + entity);
 		changeSetPersister.persistState(entity, entity.getChangeSet());
 		changeSetTxStatus = 0;
 	}
 
+	@Override
 	public void afterCompletion(int status) {
 		logger.debug("After Completion called with status = " + status);
 		if (changeSetTxStatus == 0) {
@@ -54,20 +56,13 @@ public class ChangeSetBackedTransactionSynchronization implements TransactionSyn
 		}
 	}
 
-	public void beforeCommit(boolean readOnly) {
-	}
-
-	public void beforeCompletion() {
-	}
-
-	public void flush() {
-	}
-
+	@Override
 	public void resume() {
 		throw new IllegalStateException(
 				"ChangedSetBackedTransactionSynchronization does not support transaction suspension currently");
 	}
 
+	@Override
 	public void suspend() {
 		throw new IllegalStateException(
 				"ChangedSetBackedTransactionSynchronization does not support transaction suspension currently");

src/main/java/org/springframework/data/crossstore/ChangeSetPersister.java

@@ -15,6 +15,8 @@
  */
 package org.springframework.data.crossstore;
 
+import java.io.Serial;
+
 import org.springframework.dao.DataAccessException;
 
 /**
@@ -59,7 +61,7 @@ public interface ChangeSetPersister<K> {
 	 */
 	class NotFoundException extends Exception {
 
-		private static final long serialVersionUID = -8604207973816331140L;
+		private static final @Serial long serialVersionUID = -8604207973816331140L;
 	}
 
 }

src/main/java/org/springframework/data/domain/AbstractAggregateRoot.java

@@ -21,6 +21,7 @@ import java.util.Collections;
 import java.util.List;
 
 import org.springframework.data.annotation.Transient;
+import org.springframework.lang.Contract;
 import org.springframework.util.Assert;
 
 /**
@@ -76,6 +77,7 @@ public class AbstractAggregateRoot<A extends AbstractAggregateRoot<A>> {
 	 * @return the aggregate
 	 */
 	@SuppressWarnings("unchecked")
+	@Contract("_ -> this")
 	protected final A andEventsFrom(A aggregate) {
 
 		Assert.notNull(aggregate, "Aggregate must not be null");
@@ -86,15 +88,16 @@ public class AbstractAggregateRoot<A extends AbstractAggregateRoot<A>> {
 	}
 
 	/**
-	 * Adds the given event to the aggregate for later publication
-	 * when calling a Spring Data repository's save or delete method.
-	 * Does the same as {@link #registerEvent(Object)} but returns the aggregate instead of the event.
+	 * Adds the given event to the aggregate for later publication when calling a Spring Data repository's {@code save} or
+	 * {@code delete} method. Does the same as {@link #registerEvent(Object)} but returns the aggregate instead of the
+	 * event.
 	 *
 	 * @param event must not be {@literal null}.
 	 * @return the aggregate
 	 * @see #registerEvent(Object)
 	 */
 	@SuppressWarnings("unchecked")
+	@Contract("_ -> this")
 	protected final A andEvent(Object event) {
 
 		registerEvent(event);

src/main/java/org/springframework/data/domain/AbstractPageRequest.java

@@ -15,8 +15,11 @@
  */
 package org.springframework.data.domain;
 
+import java.io.Serial;
 import java.io.Serializable;
 
+import org.springframework.util.ObjectUtils;
+
 /**
  * Abstract Java Bean implementation of {@code Pageable}.
  *
@@ -28,7 +31,7 @@ import java.io.Serializable;
  */
 public abstract class AbstractPageRequest implements Pageable, Serializable {
 
-	private static final long serialVersionUID = 1232825578694716871L;
+	private static final @Serial long serialVersionUID = 1232825578694716871L;
 
 	private final int pageNumber;
 	private final int pageSize;
@@ -85,7 +88,7 @@ public abstract class AbstractPageRequest implements Pageable, Serializable {
 	/**
 	 * Returns the {@link Pageable} requesting the previous {@link Page}.
 	 *
-	 * @return
+	 * @return the previous {@link Pageable}
 	 */
 	public abstract Pageable previous();
 
@@ -93,29 +96,21 @@ public abstract class AbstractPageRequest implements Pageable, Serializable {
 	public abstract Pageable first();
 
 	@Override
-	public int hashCode() {
-
-		final int prime = 31;
-		int result = 1;
-
-		result = prime * result + pageNumber;
-		result = prime * result + pageSize;
-
-		return result;
-	}
-
-	@Override
-	public boolean equals(Object obj) {
-
-		if (this == obj) {
+	public boolean equals(Object o) {
+		if (this == o) {
 			return true;
 		}
-
-		if (obj == null || getClass() != obj.getClass()) {
+		if (!(o instanceof AbstractPageRequest that)) {
+			return false;
+		}
+		if (pageNumber != that.pageNumber) {
 			return false;
 		}
+		return pageSize == that.pageSize;
+	}
 
-		AbstractPageRequest other = (AbstractPageRequest) obj;
-		return pageNumber == other.pageNumber && pageSize == other.pageSize;
+	@Override
+	public int hashCode() {
+		return ObjectUtils.nullSafeHash(pageNumber, pageSize);
 	}
 }

src/main/java/org/springframework/data/domain/Auditable.java

@@ -18,6 +18,8 @@ package org.springframework.data.domain;
 import java.time.temporal.TemporalAccessor;
 import java.util.Optional;
 
+import org.springframework.lang.Nullable;
+
 /**
  * Interface for auditable entities. Allows storing and retrieving creation and modification information. The changing
  * instance (typically some user) is to be defined by a generics definition.
@@ -40,7 +42,7 @@ public interface Auditable<U, ID, T extends TemporalAccessor> extends Persistabl
 	 *
 	 * @param createdBy the creating entity to set
 	 */
-	void setCreatedBy(U createdBy);
+	void setCreatedBy(@Nullable U createdBy);
 
 	/**
 	 * Returns the creation date of the entity.
@@ -68,7 +70,7 @@ public interface Auditable<U, ID, T extends TemporalAccessor> extends Persistabl
 	 *
 	 * @param lastModifiedBy the last modifying entity to set
 	 */
-	void setLastModifiedBy(U lastModifiedBy);
+	void setLastModifiedBy(@Nullable U lastModifiedBy);
 
 	/**
 	 * Returns the date of the last modification.

src/main/java/org/springframework/data/domain/Chunk.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.data.domain;
 
+import java.io.Serial;
 import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -24,6 +25,7 @@ import java.util.function.Function;
 import java.util.stream.Collectors;
 
 import org.springframework.util.Assert;
+import org.springframework.util.ObjectUtils;
 
 /**
  * A chunk of data restricted by the configured {@link Pageable}.
@@ -34,9 +36,9 @@ import org.springframework.util.Assert;
  */
 abstract class Chunk<T> implements Slice<T>, Serializable {
 
-	private static final long serialVersionUID = 867755909294344406L;
+	private static final @Serial long serialVersionUID = 867755909294344406L;
 
-	private final List<T> content = new ArrayList<>();
+	private final List<T> content;
 	private final Pageable pageable;
 
 	/**
@@ -50,7 +52,7 @@ abstract class Chunk<T> implements Slice<T>, Serializable {
 		Assert.notNull(content, "Content must not be null");
 		Assert.notNull(pageable, "Pageable must not be null");
 
-		this.content.addAll(content);
+		this.content = new ArrayList<>(content);
 		this.pageable = pageable;
 	}
 
@@ -114,6 +116,7 @@ abstract class Chunk<T> implements Slice<T>, Serializable {
 		return pageable.getSort();
 	}
 
+	@Override
 	public Iterator<T> iterator() {
 		return content.iterator();
 	}
@@ -128,34 +131,27 @@ abstract class Chunk<T> implements Slice<T>, Serializable {
 
 		Assert.notNull(converter, "Function must not be null");
 
-		return this.stream().map(converter::apply).collect(Collectors.toList());
+		return this.stream().map(converter).collect(Collectors.toList());
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(Object o) {
 
-		if (this == obj) {
+		if (this == o) {
 			return true;
 		}
-
-		if (!(obj instanceof Chunk<?> that)) {
+		if (!(o instanceof Chunk<?> chunk)) {
 			return false;
 		}
-
-		boolean contentEqual = this.content.equals(that.content);
-		boolean pageableEqual = this.pageable.equals(that.pageable);
-
-		return contentEqual && pageableEqual;
+		if (!ObjectUtils.nullSafeEquals(content, chunk.content)) {
+			return false;
+		}
+		return ObjectUtils.nullSafeEquals(pageable, chunk.pageable);
 	}
 
 	@Override
 	public int hashCode() {
-
-		int result = 17;
-
-		result += 31 * pageable.hashCode();
-		result += 31 * content.hashCode();
-
-		return result;
+		return ObjectUtils.nullSafeHash(content, pageable);
 	}
+
 }

src/main/java/org/springframework/data/domain/DomainEvents.java

@@ -35,4 +35,5 @@ import org.springframework.aot.hint.annotation.Reflective;
 @Reflective
 @Retention(RetentionPolicy.RUNTIME)
 @Target({ ElementType.METHOD, ElementType.ANNOTATION_TYPE })
-public @interface DomainEvents {}
+public @interface DomainEvents {
+}

src/main/java/org/springframework/data/domain/Example.java

@@ -33,7 +33,7 @@ public interface Example<T> {
 	 * Create a new {@link Example} including all non-null properties by default.
 	 *
 	 * @param probe must not be {@literal null}.
-	 * @return
+	 * @return a new {@link Example} for {@code probe}.
 	 */
 	static <T> Example<T> of(T probe) {
 		return new TypedExample<>(probe, ExampleMatcher.matching());
@@ -44,7 +44,7 @@ public interface Example<T> {
 	 *
 	 * @param probe must not be {@literal null}.
 	 * @param matcher must not be {@literal null}.
-	 * @return
+	 * @return a new {@link Example} for {@code probe} and {@link ExampleMatcher}.
 	 */
 	static <T> Example<T> of(T probe, ExampleMatcher matcher) {
 		return new TypedExample<>(probe, matcher);
@@ -68,7 +68,7 @@ public interface Example<T> {
 	 * Get the actual type for the probe used. This is usually the given class, but the original class in case of a
 	 * CGLIB-generated subclass.
 	 *
-	 * @return
+	 * @return the underlying probe type, potentially an unwrapped proxy.
 	 * @see ProxyUtils#getUserClass(Class)
 	 */
 	@SuppressWarnings("unchecked")

src/main/java/org/springframework/data/domain/ExampleMatcher.java

@@ -22,6 +22,8 @@ import java.util.Optional;
 import java.util.Set;
 import java.util.function.Function;
 
+import org.springframework.lang.CheckReturnValue;
+import org.springframework.lang.Contract;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
@@ -81,6 +83,8 @@ public interface ExampleMatcher {
 	 * @param ignoredPaths must not be {@literal null} and not empty.
 	 * @return new instance of {@link ExampleMatcher}.
 	 */
+	@Contract("_ -> new")
+	@CheckReturnValue
 	ExampleMatcher withIgnorePaths(String... ignoredPaths);
 
 	/**
@@ -90,6 +94,8 @@ public interface ExampleMatcher {
 	 * @param defaultStringMatcher must not be {@literal null}.
 	 * @return new instance of {@link ExampleMatcher}.
 	 */
+	@Contract("_ -> new")
+	@CheckReturnValue
 	ExampleMatcher withStringMatcher(StringMatcher defaultStringMatcher);
 
 	/**
@@ -98,6 +104,8 @@ public interface ExampleMatcher {
 	 *
 	 * @return new instance of {@link ExampleMatcher}.
 	 */
+	@Contract("-> new")
+	@CheckReturnValue
 	default ExampleMatcher withIgnoreCase() {
 		return withIgnoreCase(true);
 	}
@@ -106,9 +114,11 @@ public interface ExampleMatcher {
 	 * Returns a copy of this {@link ExampleMatcher} with {@code defaultIgnoreCase}. This instance is immutable and
 	 * unaffected by this method call.
 	 *
-	 * @param defaultIgnoreCase
+	 * @param defaultIgnoreCase {@literal true} to ignore case by default.
 	 * @return new instance of {@link ExampleMatcher}.
 	 */
+	@Contract("_ -> new")
+	@CheckReturnValue
 	ExampleMatcher withIgnoreCase(boolean defaultIgnoreCase);
 
 	/**
@@ -119,6 +129,8 @@ public interface ExampleMatcher {
 	 * @param matcherConfigurer callback to configure a {@link GenericPropertyMatcher}, must not be {@literal null}.
 	 * @return new instance of {@link ExampleMatcher}.
 	 */
+	@Contract("_, _ -> new")
+	@CheckReturnValue
 	default ExampleMatcher withMatcher(String propertyPath, MatcherConfigurer<GenericPropertyMatcher> matcherConfigurer) {
 
 		Assert.hasText(propertyPath, "PropertyPath must not be empty");
@@ -138,6 +150,8 @@ public interface ExampleMatcher {
 	 * @param genericPropertyMatcher callback to configure a {@link GenericPropertyMatcher}, must not be {@literal null}.
 	 * @return new instance of {@link ExampleMatcher}.
 	 */
+	@Contract("_, _ -> new")
+	@CheckReturnValue
 	ExampleMatcher withMatcher(String propertyPath, GenericPropertyMatcher genericPropertyMatcher);
 
 	/**
@@ -148,6 +162,8 @@ public interface ExampleMatcher {
 	 * @param propertyValueTransformer must not be {@literal null}.
 	 * @return new instance of {@link ExampleMatcher}.
 	 */
+	@Contract("_, _ -> new")
+	@CheckReturnValue
 	ExampleMatcher withTransformer(String propertyPath, PropertyValueTransformer propertyValueTransformer);
 
 	/**
@@ -157,6 +173,8 @@ public interface ExampleMatcher {
 	 * @param propertyPaths must not be {@literal null} and not empty.
 	 * @return new instance of {@link ExampleMatcher}.
 	 */
+	@Contract("_ -> new")
+	@CheckReturnValue
 	ExampleMatcher withIgnoreCase(String... propertyPaths);
 
 	/**
@@ -165,6 +183,8 @@ public interface ExampleMatcher {
 	 *
 	 * @return new instance of {@link ExampleMatcher}.
 	 */
+	@Contract("-> new")
+	@CheckReturnValue
 	default ExampleMatcher withIncludeNullValues() {
 		return withNullHandler(NullHandler.INCLUDE);
 	}
@@ -175,6 +195,8 @@ public interface ExampleMatcher {
 	 *
 	 * @return new instance of {@link ExampleMatcher}.
 	 */
+	@Contract("-> new")
+	@CheckReturnValue
 	default ExampleMatcher withIgnoreNullValues() {
 		return withNullHandler(NullHandler.IGNORE);
 	}
@@ -186,19 +208,21 @@ public interface ExampleMatcher {
 	 * @param nullHandler must not be {@literal null}.
 	 * @return new instance of {@link ExampleMatcher}.
 	 */
+	@Contract("_ -> new")
+	@CheckReturnValue
 	ExampleMatcher withNullHandler(NullHandler nullHandler);
 
 	/**
-	 * Get defined null handling.
+	 * Get the defined null handling.
 	 *
-	 * @return never {@literal null}
+	 * @return the defined null handling.
 	 */
 	NullHandler getNullHandler();
 
 	/**
-	 * Get defined {@link ExampleMatcher.StringMatcher}.
+	 * Get the defined {@link ExampleMatcher.StringMatcher}.
 	 *
-	 * @return never {@literal null}.
+	 * @return the defined {@link ExampleMatcher.StringMatcher}.
 	 */
 	StringMatcher getDefaultStringMatcher();
 
@@ -226,10 +250,10 @@ public interface ExampleMatcher {
 	PropertySpecifiers getPropertySpecifiers();
 
 	/**
-	 * Returns whether all of the predicates of the {@link Example} are supposed to match. If {@literal false} is
-	 * returned, it's sufficient if any of the predicates derived from the {@link Example} match.
+	 * Returns whether all the predicates of the {@link Example} are supposed to match. If {@literal false} is returned,
+	 * it's sufficient if any of the predicates derived from the {@link Example} match.
 	 *
-	 * @return whether all of the predicates of the {@link Example} are supposed to match or any of them is sufficient.
+	 * @return whether all the predicates of the {@link Example} are supposed to match or any of them is sufficient.
 	 */
 	default boolean isAllMatching() {
 		return getMatchMode().equals(MatchMode.ALL);
@@ -293,8 +317,7 @@ public interface ExampleMatcher {
 		 * Creates a new {@link GenericPropertyMatcher} with a {@link StringMatcher} and {@code ignoreCase}.
 		 *
 		 * @param stringMatcher must not be {@literal null}.
-		 * @param ignoreCase
-		 * @return
+		 * @param ignoreCase {@literal true} to ignore case.
 		 */
 		public static GenericPropertyMatcher of(StringMatcher stringMatcher, boolean ignoreCase) {
 			return new GenericPropertyMatcher().stringMatcher(stringMatcher).ignoreCase(ignoreCase);
@@ -304,7 +327,6 @@ public interface ExampleMatcher {
 		 * Creates a new {@link GenericPropertyMatcher} with a {@link StringMatcher} and {@code ignoreCase}.
 		 *
 		 * @param stringMatcher must not be {@literal null}.
-		 * @return
 		 */
 		public static GenericPropertyMatcher of(StringMatcher stringMatcher) {
 			return new GenericPropertyMatcher().stringMatcher(stringMatcher);
@@ -312,9 +334,8 @@ public interface ExampleMatcher {
 
 		/**
 		 * Sets ignores case to {@literal true}.
-		 *
-		 * @return
 		 */
+		@Contract(" -> this")
 		public GenericPropertyMatcher ignoreCase() {
 
 			this.ignoreCase = true;
@@ -324,9 +345,9 @@ public interface ExampleMatcher {
 		/**
 		 * Sets ignores case to {@code ignoreCase}.
 		 *
-		 * @param ignoreCase
-		 * @return
+		 * @param ignoreCase {@literal true} to ignore case.
 		 */
+		@Contract("_ -> this")
 		public GenericPropertyMatcher ignoreCase(boolean ignoreCase) {
 
 			this.ignoreCase = ignoreCase;
@@ -335,9 +356,8 @@ public interface ExampleMatcher {
 
 		/**
 		 * Sets ignores case to {@literal false}.
-		 *
-		 * @return
 		 */
+		@Contract(" -> this")
 		public GenericPropertyMatcher caseSensitive() {
 
 			this.ignoreCase = false;
@@ -346,9 +366,8 @@ public interface ExampleMatcher {
 
 		/**
 		 * Sets string matcher to {@link StringMatcher#CONTAINING}.
-		 *
-		 * @return
 		 */
+		@Contract(" -> this")
 		public GenericPropertyMatcher contains() {
 
 			this.stringMatcher = StringMatcher.CONTAINING;
@@ -357,9 +376,8 @@ public interface ExampleMatcher {
 
 		/**
 		 * Sets string matcher to {@link StringMatcher#ENDING}.
-		 *
-		 * @return
 		 */
+		@Contract(" -> this")
 		public GenericPropertyMatcher endsWith() {
 
 			this.stringMatcher = StringMatcher.ENDING;
@@ -368,9 +386,8 @@ public interface ExampleMatcher {
 
 		/**
 		 * Sets string matcher to {@link StringMatcher#STARTING}.
-		 *
-		 * @return
 		 */
+		@Contract(" -> this")
 		public GenericPropertyMatcher startsWith() {
 
 			this.stringMatcher = StringMatcher.STARTING;
@@ -379,9 +396,8 @@ public interface ExampleMatcher {
 
 		/**
 		 * Sets string matcher to {@link StringMatcher#EXACT}.
-		 *
-		 * @return
 		 */
+		@Contract(" -> this")
 		public GenericPropertyMatcher exact() {
 
 			this.stringMatcher = StringMatcher.EXACT;
@@ -390,9 +406,8 @@ public interface ExampleMatcher {
 
 		/**
 		 * Sets string matcher to {@link StringMatcher#DEFAULT}.
-		 *
-		 * @return
 		 */
+		@Contract(" -> this")
 		public GenericPropertyMatcher storeDefaultMatching() {
 
 			this.stringMatcher = StringMatcher.DEFAULT;
@@ -401,9 +416,8 @@ public interface ExampleMatcher {
 
 		/**
 		 * Sets string matcher to {@link StringMatcher#REGEX}.
-		 *
-		 * @return
 		 */
+		@Contract(" -> this")
 		public GenericPropertyMatcher regex() {
 
 			this.stringMatcher = StringMatcher.REGEX;
@@ -414,8 +428,8 @@ public interface ExampleMatcher {
 		 * Sets string matcher to {@code stringMatcher}.
 		 *
 		 * @param stringMatcher must not be {@literal null}.
-		 * @return
 		 */
+		@Contract("_ -> this")
 		public GenericPropertyMatcher stringMatcher(StringMatcher stringMatcher) {
 
 			Assert.notNull(stringMatcher, "StringMatcher must not be null");
@@ -427,8 +441,8 @@ public interface ExampleMatcher {
 		 * Sets the {@link PropertyValueTransformer} to {@code propertyValueTransformer}.
 		 *
 		 * @param propertyValueTransformer must not be {@literal null}.
-		 * @return
 		 */
+		@Contract("_ -> this")
 		public GenericPropertyMatcher transform(PropertyValueTransformer propertyValueTransformer) {
 
 			Assert.notNull(propertyValueTransformer, "PropertyValueTransformer must not be null");
@@ -463,10 +477,7 @@ public interface ExampleMatcher {
 
 		@Override
 		public int hashCode() {
-			int result = ObjectUtils.nullSafeHashCode(stringMatcher);
-			result = 31 * result + ObjectUtils.nullSafeHashCode(ignoreCase);
-			result = 31 * result + ObjectUtils.nullSafeHashCode(valueTransformer);
-			return result;
+			return ObjectUtils.nullSafeHash(stringMatcher, ignoreCase, valueTransformer);
 		}
 	}
 
@@ -478,9 +489,7 @@ public interface ExampleMatcher {
 	class GenericPropertyMatchers {
 
 		/**
-		 * Creates a {@link GenericPropertyMatcher} that matches string case insensitive.
-		 *
-		 * @return
+		 * Creates a {@link GenericPropertyMatcher} that matches string case-insensitive.
 		 */
 		public static GenericPropertyMatcher ignoreCase() {
 			return new GenericPropertyMatcher().ignoreCase();
@@ -488,8 +497,6 @@ public interface ExampleMatcher {
 
 		/**
 		 * Creates a {@link GenericPropertyMatcher} that matches string case-sensitive.
-		 *
-		 * @return
 		 */
 		public static GenericPropertyMatcher caseSensitive() {
 			return new GenericPropertyMatcher().caseSensitive();
@@ -497,8 +504,6 @@ public interface ExampleMatcher {
 
 		/**
 		 * Creates a {@link GenericPropertyMatcher} that matches string using {@link StringMatcher#CONTAINING}.
-		 *
-		 * @return
 		 */
 		public static GenericPropertyMatcher contains() {
 			return new GenericPropertyMatcher().contains();
@@ -506,8 +511,6 @@ public interface ExampleMatcher {
 
 		/**
 		 * Creates a {@link GenericPropertyMatcher} that matches string using {@link StringMatcher#ENDING}.
-		 *
-		 * @return
 		 */
 		public static GenericPropertyMatcher endsWith() {
 			return new GenericPropertyMatcher().endsWith();
@@ -516,8 +519,6 @@ public interface ExampleMatcher {
 
 		/**
 		 * Creates a {@link GenericPropertyMatcher} that matches string using {@link StringMatcher#STARTING}.
-		 *
-		 * @return
 		 */
 		public static GenericPropertyMatcher startsWith() {
 			return new GenericPropertyMatcher().startsWith();
@@ -525,8 +526,6 @@ public interface ExampleMatcher {
 
 		/**
 		 * Creates a {@link GenericPropertyMatcher} that matches string using {@link StringMatcher#EXACT}.
-		 *
-		 * @return
 		 */
 		public static GenericPropertyMatcher exact() {
 			return new GenericPropertyMatcher().exact();
@@ -534,8 +533,6 @@ public interface ExampleMatcher {
 
 		/**
 		 * Creates a {@link GenericPropertyMatcher} that matches string using {@link StringMatcher#DEFAULT}.
-		 *
-		 * @return
 		 */
 		public static GenericPropertyMatcher storeDefaultMatching() {
 			return new GenericPropertyMatcher().storeDefaultMatching();
@@ -543,8 +540,6 @@ public interface ExampleMatcher {
 
 		/**
 		 * Creates a {@link GenericPropertyMatcher} that matches string using {@link StringMatcher#REGEX}.
-		 *
-		 * @return
 		 */
 		public static GenericPropertyMatcher regex() {
 			return new GenericPropertyMatcher().regex();
@@ -648,8 +643,9 @@ public interface ExampleMatcher {
 		 * {@link StringMatcher} in the returned instance.
 		 *
 		 * @param stringMatcher must not be {@literal null}.
-		 * @return
 		 */
+		@Contract("_ -> new")
+		@CheckReturnValue
 		public PropertySpecifier withStringMatcher(StringMatcher stringMatcher) {
 
 			Assert.notNull(stringMatcher, "StringMatcher must not be null");
@@ -660,9 +656,10 @@ public interface ExampleMatcher {
 		 * Creates a new {@link PropertySpecifier} containing all values from the current instance and sets
 		 * {@code ignoreCase}.
 		 *
-		 * @param ignoreCase must not be {@literal null}.
-		 * @return
+		 * @param ignoreCase {@literal true} to ignore case.
 		 */
+		@Contract("_ -> new")
+		@CheckReturnValue
 		public PropertySpecifier withIgnoreCase(boolean ignoreCase) {
 			return new PropertySpecifier(this.path, this.stringMatcher, ignoreCase, this.valueTransformer);
 		}
@@ -672,8 +669,9 @@ public interface ExampleMatcher {
 		 * {@link PropertyValueTransformer} in the returned instance.
 		 *
 		 * @param valueTransformer must not be {@literal null}.
-		 * @return
 		 */
+		@Contract("_ -> new")
+		@CheckReturnValue
 		public PropertySpecifier withValueTransformer(PropertyValueTransformer valueTransformer) {
 
 			Assert.notNull(valueTransformer, "PropertyValueTransformer must not be null");
@@ -719,7 +717,7 @@ public interface ExampleMatcher {
 		/**
 		 * Transforms a given source using the {@link PropertyValueTransformer}.
 		 *
-		 * @param source
+		 * @param source source value to transform.
 		 * @return
 		 */
 		public Optional<Object> transformValue(Optional<Object> source) {
@@ -753,11 +751,7 @@ public interface ExampleMatcher {
 
 		@Override
 		public int hashCode() {
-			int result = ObjectUtils.nullSafeHashCode(path);
-			result = 31 * result + ObjectUtils.nullSafeHashCode(stringMatcher);
-			result = 31 * result + ObjectUtils.nullSafeHashCode(ignoreCase);
-			result = 31 * result + ObjectUtils.nullSafeHashCode(valueTransformer);
-			return result;
+			return ObjectUtils.nullSafeHash(path, stringMatcher, ignoreCase, valueTransformer);
 		}
 
 		protected boolean canEqual(final Object other) {

src/main/java/org/springframework/data/domain/Limit.java

@@ -110,7 +110,7 @@ public sealed interface Limit permits Limited, Unlimited {
 
 		@Override
 		public int hashCode() {
-			return max ^ max >>> 32;
+			return max;
 		}
 	}
 

src/main/java/org/springframework/data/domain/OffsetScrollPosition.java

@@ -123,6 +123,7 @@ public final class OffsetScrollPosition implements ScrollPosition {
 		return offset == -1;
 	}
 
+
 	@Override
 	public boolean equals(@Nullable Object o) {
 

src/main/java/org/springframework/data/domain/Page.java

@@ -29,8 +29,6 @@ public interface Page<T> extends Slice<T> {
 
 	/**
 	 * Creates a new empty {@link Page}.
-	 *
-	 * @return
 	 * @since 2.0
 	 */
 	static <T> Page<T> empty() {
@@ -41,7 +39,7 @@ public interface Page<T> extends Slice<T> {
 	 * Creates a new empty {@link Page} for the given {@link Pageable}.
 	 *
 	 * @param pageable must not be {@literal null}.
-	 * @return
+	 * @return a new, empty {@link Page} wrapping the given {@link Pageable}.
 	 * @since 2.0
 	 */
 	static <T> Page<T> empty(Pageable pageable) {

src/main/java/org/springframework/data/domain/PageImpl.java

@@ -15,10 +15,12 @@
  */
 package org.springframework.data.domain;
 
+import java.io.Serial;
 import java.util.List;
 import java.util.function.Function;
 
 import org.springframework.lang.Nullable;
+import org.springframework.util.CollectionUtils;
 
 /**
  * Basic {@code Page} implementation.
@@ -29,7 +31,7 @@ import org.springframework.lang.Nullable;
  */
 public class PageImpl<T> extends Chunk<T> implements Page<T> {
 
-	private static final long serialVersionUID = 867755909294344406L;
+	private static final @Serial long serialVersionUID = 867755909294344406L;
 
 	private final long total;
 
@@ -58,7 +60,7 @@ public class PageImpl<T> extends Chunk<T> implements Page<T> {
 	 * @param content must not be {@literal null}.
 	 */
 	public PageImpl(List<T> content) {
-		this(content, Pageable.unpaged(), null == content ? 0 : content.size());
+		this(content, Pageable.unpaged(), CollectionUtils.isEmpty(content) ? 0 : content.size());
 	}
 
 	@Override
@@ -86,19 +88,6 @@ public class PageImpl<T> extends Chunk<T> implements Page<T> {
 		return new PageImpl<>(getConvertedContent(converter), getPageable(), total);
 	}
 
-	@Override
-	public String toString() {
-
-		String contentType = "UNKNOWN";
-		List<T> content = getContent();
-
-		if (!content.isEmpty() && content.get(0) != null) {
-			contentType = content.get(0).getClass().getName();
-		}
-
-		return String.format("Page %s of %d containing %s instances", getNumber() + 1, getTotalPages(), contentType);
-	}
-
 	@Override
 	public boolean equals(@Nullable Object obj) {
 
@@ -115,12 +104,19 @@ public class PageImpl<T> extends Chunk<T> implements Page<T> {
 
 	@Override
 	public int hashCode() {
+		return 31 * super.hashCode() + Long.hashCode(total);
+	}
 
-		int result = 17;
+	@Override
+	public String toString() {
 
-		result += 31 * (int) (total ^ total >>> 32);
-		result += 31 * super.hashCode();
+		String contentType = "UNKNOWN";
+		List<T> content = getContent();
 
-		return result;
+		if (!content.isEmpty() && content.get(0) != null) {
+			contentType = content.get(0).getClass().getName();
+		}
+
+		return String.format("Page %s of %d containing %s instances", getNumber() + 1, getTotalPages(), contentType);
 	}
 }

src/main/java/org/springframework/data/domain/PageRequest.java

@@ -15,9 +15,14 @@
  */
 package org.springframework.data.domain;
 
+import java.io.Serial;
+
 import org.springframework.data.domain.Sort.Direction;
+import org.springframework.lang.CheckReturnValue;
+import org.springframework.lang.Contract;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.ObjectUtils;
 
 /**
  * Basic Java Bean implementation of {@link Pageable}.
@@ -30,7 +35,7 @@ import org.springframework.util.Assert;
  */
 public class PageRequest extends AbstractPageRequest {
 
-	private static final long serialVersionUID = -4541509938956089562L;
+	private static final @Serial long serialVersionUID = -4541509938956089562L;
 
 	private final Sort sort;
 
@@ -103,42 +108,36 @@ public class PageRequest extends AbstractPageRequest {
 	}
 
 	@Override
+	@Contract("_ -> new")
+	@CheckReturnValue
 	public PageRequest next() {
 		return new PageRequest(getPageNumber() + 1, getPageSize(), getSort());
 	}
 
 	@Override
+	@Contract("_ -> new")
+	@CheckReturnValue
 	public PageRequest previous() {
 		return getPageNumber() == 0 ? this : new PageRequest(getPageNumber() - 1, getPageSize(), getSort());
 	}
 
 	@Override
+	@Contract("_ -> new")
+	@CheckReturnValue
 	public PageRequest first() {
 		return new PageRequest(0, getPageSize(), getSort());
 	}
 
-	@Override
-	public boolean equals(@Nullable Object obj) {
-
-		if (this == obj) {
-			return true;
-		}
-
-		if (!(obj instanceof PageRequest that)) {
-			return false;
-		}
-
-		return super.equals(that) && sort.equals(that.sort);
-	}
-
 	/**
 	 * Creates a new {@link PageRequest} with {@code pageNumber} applied.
 	 *
-	 * @param pageNumber
+	 * @param pageNumber the page number to apply.
 	 * @return a new {@link PageRequest}.
 	 * @since 2.5
 	 */
 	@Override
+	@Contract("_ -> new")
+	@CheckReturnValue
 	public PageRequest withPage(int pageNumber) {
 		return new PageRequest(pageNumber, getPageSize(), getSort());
 	}
@@ -151,6 +150,8 @@ public class PageRequest extends AbstractPageRequest {
 	 * @return a new {@link PageRequest}.
 	 * @since 2.5
 	 */
+	@Contract("_, _ -> new")
+	@CheckReturnValue
 	public PageRequest withSort(Direction direction, String... properties) {
 		return new PageRequest(getPageNumber(), getPageSize(), Sort.by(direction, properties));
 	}
@@ -162,13 +163,30 @@ public class PageRequest extends AbstractPageRequest {
 	 * @return a new {@link PageRequest}.
 	 * @since 2.5
 	 */
+	@Contract("_ -> new")
+	@CheckReturnValue
 	public PageRequest withSort(Sort sort) {
 		return new PageRequest(getPageNumber(), getPageSize(), sort);
 	}
 
+	@Override
+	public boolean equals(Object o) {
+
+		if (this == o) {
+			return true;
+		}
+		if (!(o instanceof PageRequest that)) {
+			return false;
+		}
+		if (!super.equals(o)) {
+			return false;
+		}
+		return ObjectUtils.nullSafeEquals(sort, that.sort);
+	}
+
 	@Override
 	public int hashCode() {
-		return 31 * super.hashCode() + sort.hashCode();
+		return super.hashCode() * 31 + ObjectUtils.nullSafeHash(sort);
 	}
 
 	@Override

src/main/java/org/springframework/data/domain/Pageable.java

@@ -17,6 +17,8 @@ package org.springframework.data.domain;
 
 import java.util.Optional;
 
+import org.springframework.lang.CheckReturnValue;
+import org.springframework.lang.Contract;
 import org.springframework.util.Assert;
 
 /**
@@ -30,8 +32,6 @@ public interface Pageable {
 
 	/**
 	 * Returns a {@link Pageable} instance representing no pagination setup.
-	 *
-	 * @return
 	 */
 	static Pageable unpaged() {
 		return unpaged(Sort.unsorted());
@@ -41,7 +41,8 @@ public interface Pageable {
 	 * Returns a {@link Pageable} instance representing no pagination setup having a defined result {@link Sort order}.
 	 *
 	 * @param sort must not be {@literal null}, use {@link Sort#unsorted()} if needed.
-	 * @return never {@literal null}.
+	 * @return an unpaged {@link Pageable} instance representing no pagination setup considering the given {@link Sort}
+	 *         order.
 	 * @since 3.2
 	 */
 	static Pageable unpaged(Sort sort) {
@@ -62,7 +63,7 @@ public interface Pageable {
 	/**
 	 * Returns whether the current {@link Pageable} contains pagination information.
 	 *
-	 * @return
+	 * @return {@literal true} if the current {@link Pageable} contains pagination information.
 	 */
 	default boolean isPaged() {
 		return true;
@@ -71,7 +72,7 @@ public interface Pageable {
 	/**
 	 * Returns whether the current {@link Pageable} does not contain pagination information.
 	 *
-	 * @return
+	 * @return {@literal true} if the current {@link Pageable} does not contain pagination information.
 	 */
 	default boolean isUnpaged() {
 		return !isPaged();
@@ -107,7 +108,7 @@ public interface Pageable {
 	/**
 	 * Returns the sorting parameters.
 	 *
-	 * @return
+	 * @return the sorting order.
 	 */
 	Sort getSort();
 
@@ -115,7 +116,7 @@ public interface Pageable {
 	 * Returns the current {@link Sort} or the given one if the current one is unsorted.
 	 *
 	 * @param sort must not be {@literal null}.
-	 * @return
+	 * @return the current {@link Sort} or the {@code sort} one if the current one is unsorted.
 	 */
 	default Sort getSortOr(Sort sort) {
 
@@ -127,47 +128,55 @@ public interface Pageable {
 	/**
 	 * Returns the {@link Pageable} requesting the next {@link Page}.
 	 *
-	 * @return
+	 * @return the {@link Pageable} requesting the next {@link Page}.
 	 */
+	@Contract("_ -> new")
+	@CheckReturnValue
 	Pageable next();
 
 	/**
 	 * Returns the previous {@link Pageable} or the first {@link Pageable} if the current one already is the first one.
 	 *
-	 * @return
+	 * @return the previous {@link Pageable} or the first {@link Pageable} if the current one already is the first one.
 	 */
+	@Contract("_ -> new")
+	@CheckReturnValue
 	Pageable previousOrFirst();
 
 	/**
 	 * Returns the {@link Pageable} requesting the first page.
 	 *
-	 * @return
+	 * @return the {@link Pageable} requesting the first page.
 	 */
+	@Contract("_ -> new")
+	@CheckReturnValue
 	Pageable first();
 
 	/**
 	 * Creates a new {@link Pageable} with {@code pageNumber} applied.
 	 *
-	 * @param pageNumber
+	 * @param pageNumber the page numbe, zero-based.
 	 * @return a new {@link PageRequest} or throws {@link UnsupportedOperationException} if the object is
 	 *         {@link #isUnpaged()} and the {@code pageNumber} is not zero.
 	 * @since 2.5
 	 * @throws UnsupportedOperationException if the object is {@link #isUnpaged()}.
 	 */
+	@Contract("_ -> new")
+	@CheckReturnValue
 	Pageable withPage(int pageNumber);
 
 	/**
 	 * Returns whether there's a previous {@link Pageable} we can access from the current one. Will return
 	 * {@literal false} in case the current {@link Pageable} already refers to the first page.
 	 *
-	 * @return
+	 * @return {@literal true} if there's a previous {@link Pageable} we can access from the current one.
 	 */
 	boolean hasPrevious();
 
 	/**
 	 * Returns an {@link Optional} so that it can easily be mapped on.
 	 *
-	 * @return
+	 * @return an {@link Optional} so that it can easily be mapped on.
 	 */
 	default Optional<Pageable> toOptional() {
 		return isUnpaged() ? Optional.empty() : Optional.of(this);
@@ -177,7 +186,7 @@ public interface Pageable {
 	 * Returns an {@link Limit} from this pageable if the page request {@link #isPaged() is paged} or
 	 * {@link Limit#unlimited()} otherwise.
 	 *
-	 * @return
+	 * @return a {@link Limit} object based on the current page size.
 	 * @since 3.2
 	 */
 	default Limit toLimit() {
@@ -193,7 +202,7 @@ public interface Pageable {
 	 * Returns an {@link OffsetScrollPosition} from this pageable if the page request {@link #isPaged() is paged}.
 	 * <p>
 	 * Given the exclusive nature of scrolling the {@link ScrollPosition} for {@code Page(0, 10)} translates an
-	 * {@link ScrollPosition#isInitial() initial} position, where as {@code Page(1, 10)} will point to the last element of
+	 * {@link ScrollPosition#isInitial() initial} position, whereas {@code Page(1, 10)} will point to the last element of
 	 * {@code Page(0,10)} resulting in {@link ScrollPosition#offset(long) ScrollPosition(9)}.
 	 *
 	 * @return new instance of {@link OffsetScrollPosition}.

src/main/java/org/springframework/data/domain/Range.java

@@ -19,6 +19,7 @@ import java.util.Comparator;
 import java.util.Optional;
 import java.util.function.Function;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 
@@ -55,7 +56,7 @@ public final class Range<T> {
 	/**
 	 * Returns an unbounded {@link Range}.
 	 *
-	 * @return
+	 * @return an unbounded {@link Range}.
 	 * @since 2.0
 	 */
 	@SuppressWarnings("unchecked")
@@ -66,10 +67,10 @@ public final class Range<T> {
 	/**
 	 * Creates a new {@link Range} with inclusive bounds for both values.
 	 *
-	 * @param <T>
+	 * @param <T> the type of the range.
 	 * @param from must not be {@literal null}.
 	 * @param to must not be {@literal null}.
-	 * @return
+	 * @return a {@link Range} with the lower bound set inclusively and the upper bound inclusively.
 	 * @since 2.2
 	 */
 	public static <T> Range<T> closed(T from, T to) {
@@ -79,10 +80,10 @@ public final class Range<T> {
 	/**
 	 * Creates a new {@link Range} with exclusive bounds for both values.
 	 *
-	 * @param <T>
+	 * @param <T> the type of the range.
 	 * @param from must not be {@literal null}.
 	 * @param to must not be {@literal null}.
-	 * @return
+	 * @return a {@link Range} with the lower bound set exclusively and the upper bound exclusively.
 	 * @since 2.2
 	 */
 	public static <T> Range<T> open(T from, T to) {
@@ -92,10 +93,10 @@ public final class Range<T> {
 	/**
 	 * Creates a new left-open {@link Range}, i.e. left exclusive, right inclusive.
 	 *
-	 * @param <T>
+	 * @param <T> the type of the range.
 	 * @param from must not be {@literal null}.
 	 * @param to must not be {@literal null}.
-	 * @return
+	 * @return a {@link Range} with the lower bound set exclusively and the upper bound inclusively.
 	 * @since 2.2
 	 */
 	public static <T> Range<T> leftOpen(T from, T to) {
@@ -105,10 +106,10 @@ public final class Range<T> {
 	/**
 	 * Creates a new right-open {@link Range}, i.e. left inclusive, right exclusive.
 	 *
-	 * @param <T>
+	 * @param <T> the type of the range.
 	 * @param from must not be {@literal null}.
 	 * @param to must not be {@literal null}.
-	 * @return
+	 * @return a {@link Range} with the lower bound set inclusively and the upper bound exclusively.
 	 * @since 2.2
 	 */
 	public static <T> Range<T> rightOpen(T from, T to) {
@@ -119,9 +120,9 @@ public final class Range<T> {
 	 * Creates a left-unbounded {@link Range} (the left bound set to {@link Bound#unbounded()}) with the given right
 	 * bound.
 	 *
-	 * @param <T>
+	 * @param <T> the type of the range.
 	 * @param to the right {@link Bound}, must not be {@literal null}.
-	 * @return
+	 * @return a {@link Range} with the upper bound set to the given value and the lower side unbounded.
 	 * @since 2.2
 	 */
 	public static <T> Range<T> leftUnbounded(Bound<T> to) {
@@ -132,9 +133,9 @@ public final class Range<T> {
 	 * Creates a right-unbounded {@link Range} (the right bound set to {@link Bound#unbounded()}) with the given left
 	 * bound.
 	 *
-	 * @param <T>
+	 * @param <T> the type of the range.
 	 * @param from the left {@link Bound}, must not be {@literal null}.
-	 * @return
+	 * @return a {@link Range} with the lower bound set to the given value and the upper side unbounded.
 	 * @since 2.2
 	 */
 	public static <T> Range<T> rightUnbounded(Bound<T> from) {
@@ -145,7 +146,7 @@ public final class Range<T> {
 	 * Create a {@link RangeBuilder} given the lower {@link Bound}.
 	 *
 	 * @param lower must not be {@literal null}.
-	 * @return
+	 * @return a range builder to continue creating a {@link Range} from the lower bound.
 	 * @since 2.0
 	 */
 	public static <T> RangeBuilder<T> from(Bound<T> lower) {
@@ -170,9 +171,9 @@ public final class Range<T> {
 	/**
 	 * Creates a new Range with the given value as sole member.
 	 *
-	 * @param <T>
+	 * @param <T> the type of the range.>
 	 * @param value must not be {@literal null}.
-	 * @return
+	 * @return a range containing the given value.
 	 * @see Range#closed(Object, Object)
 	 */
 	public static <T> Range<T> just(T value) {
@@ -183,7 +184,7 @@ public final class Range<T> {
 	 * Returns whether the {@link Range} contains the given value.
 	 *
 	 * @param value must not be {@literal null}.
-	 * @return
+	 * @return {@literal true} if the range contains the value; {@literal false} otherwise.
 	 */
 	@SuppressWarnings({ "unchecked" })
 	public boolean contains(Comparable<T> value) {
@@ -200,7 +201,7 @@ public final class Range<T> {
 	 * Returns whether the {@link Range} contains the given value.
 	 *
 	 * @param value must not be {@literal null}.
-	 * @return
+	 * @return {@literal true} if the range contains the value; {@literal false} otherwise.
 	 * @since 3.0
 	 */
 	public boolean contains(T value, Comparator<T> comparator) {
@@ -224,7 +225,7 @@ public final class Range<T> {
 	 * @param mapper must not be {@literal null}. If the mapper returns {@code null}, then the corresponding boundary
 	 *          value represents an {@link Bound#unbounded()} boundary.
 	 * @return a new {@link Range} after applying the value to the mapper.
-	 * @param <R>
+	 * @param <R> target type of the mapping function.
 	 * @since 3.0
 	 */
 	public <R> Range<R> map(Function<? super T, ? extends R> mapper) {
@@ -248,7 +249,7 @@ public final class Range<T> {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 
 		if (this == o) {
 			return true;
@@ -267,9 +268,7 @@ public final class Range<T> {
 
 	@Override
 	public int hashCode() {
-		int result = ObjectUtils.nullSafeHashCode(lowerBound);
-		result = 31 * result + ObjectUtils.nullSafeHashCode(upperBound);
-		return result;
+		return ObjectUtils.nullSafeHash(lowerBound, upperBound);
 	}
 
 	/**
@@ -313,7 +312,6 @@ public final class Range<T> {
 		 * Creates a boundary including {@code value}.
 		 *
 		 * @param value must not be {@literal null}.
-		 * @return
 		 */
 		public static <T> Bound<T> inclusive(T value) {
 
@@ -325,7 +323,6 @@ public final class Range<T> {
 		 * Creates a boundary including {@code value}.
 		 *
 		 * @param value must not be {@literal null}.
-		 * @return
 		 */
 		public static Bound<Integer> inclusive(int value) {
 			return inclusive((Integer) value);
@@ -335,7 +332,6 @@ public final class Range<T> {
 		 * Creates a boundary including {@code value}.
 		 *
 		 * @param value must not be {@literal null}.
-		 * @return
 		 */
 		public static Bound<Long> inclusive(long value) {
 			return inclusive((Long) value);
@@ -345,7 +341,6 @@ public final class Range<T> {
 		 * Creates a boundary including {@code value}.
 		 *
 		 * @param value must not be {@literal null}.
-		 * @return
 		 */
 		public static Bound<Float> inclusive(float value) {
 			return inclusive((Float) value);
@@ -355,7 +350,6 @@ public final class Range<T> {
 		 * Creates a boundary including {@code value}.
 		 *
 		 * @param value must not be {@literal null}.
-		 * @return
 		 */
 		public static Bound<Double> inclusive(double value) {
 			return inclusive((Double) value);
@@ -365,7 +359,6 @@ public final class Range<T> {
 		 * Creates a boundary excluding {@code value}.
 		 *
 		 * @param value must not be {@literal null}.
-		 * @return
 		 */
 		public static <T> Bound<T> exclusive(T value) {
 
@@ -377,7 +370,6 @@ public final class Range<T> {
 		 * Creates a boundary excluding {@code value}.
 		 *
 		 * @param value must not be {@literal null}.
-		 * @return
 		 */
 		public static Bound<Integer> exclusive(int value) {
 			return exclusive((Integer) value);
@@ -387,7 +379,6 @@ public final class Range<T> {
 		 * Creates a boundary excluding {@code value}.
 		 *
 		 * @param value must not be {@literal null}.
-		 * @return
 		 */
 		public static Bound<Long> exclusive(long value) {
 			return exclusive((Long) value);
@@ -397,7 +388,6 @@ public final class Range<T> {
 		 * Creates a boundary excluding {@code value}.
 		 *
 		 * @param value must not be {@literal null}.
-		 * @return
 		 */
 		public static Bound<Float> exclusive(float value) {
 			return exclusive((Float) value);
@@ -407,7 +397,6 @@ public final class Range<T> {
 		 * Creates a boundary excluding {@code value}.
 		 *
 		 * @param value must not be {@literal null}.
-		 * @return
 		 */
 		public static Bound<Double> exclusive(double value) {
 			return exclusive((Double) value);
@@ -429,11 +418,6 @@ public final class Range<T> {
 					.orElse("unbounded");
 		}
 
-		@Override
-		public String toString() {
-			return value.map(Object::toString).orElse("unbounded");
-		}
-
 		public Optional<T> getValue() {
 			return this.value;
 		}
@@ -442,8 +426,33 @@ public final class Range<T> {
 			return this.inclusive;
 		}
 
+		/**
+		 * Apply a mapping {@link Function} to the boundary value.
+		 *
+		 * @param mapper must not be {@literal null}. If the mapper returns {@code null}, then the boundary value
+		 *          corresponds with {@link Bound#unbounded()}.
+		 * @return a new {@link Bound} after applying the value to the mapper.
+		 * @param <R>
+		 * @since 3.0
+		 */
+		public <R> Bound<R> map(Function<? super T, ? extends R> mapper) {
+
+			Assert.notNull(mapper, "Mapping function must not be null");
+
+			return Bound.of(value.map(mapper), inclusive);
+		}
+
+		private static <R> Bound<R> of(Optional<R> value, boolean inclusive) {
+
+			if (value.isPresent()) {
+				return new Bound<>(value, inclusive);
+			}
+
+			return unbounded();
+		}
+
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 
 			if (this == o) {
 				return true;
@@ -453,7 +462,7 @@ public final class Range<T> {
 				return false;
 			}
 
-			if (!value.isPresent() && !bound.value.isPresent()) {
+			if (value.isEmpty() && bound.value.isEmpty()) {
 				return true;
 			}
 
@@ -466,7 +475,7 @@ public final class Range<T> {
 		@Override
 		public int hashCode() {
 
-			if (!value.isPresent()) {
+			if (value.isEmpty()) {
 				return ObjectUtils.nullSafeHashCode(value);
 			}
 
@@ -475,29 +484,9 @@ public final class Range<T> {
 			return result;
 		}
 
-		/**
-		 * Apply a mapping {@link Function} to the boundary value.
-		 *
-		 * @param mapper must not be {@literal null}. If the mapper returns {@code null}, then the boundary value
-		 *          corresponds with {@link Bound#unbounded()}.
-		 * @return a new {@link Bound} after applying the value to the mapper.
-		 * @param <R>
-		 * @since 3.0
-		 */
-		public <R> Bound<R> map(Function<? super T, ? extends R> mapper) {
-
-			Assert.notNull(mapper, "Mapping function must not be null");
-
-			return Bound.of(value.map(mapper), inclusive);
-		}
-
-		private static <R> Bound<R> of(Optional<R> value, boolean inclusive) {
-
-			if (value.isPresent()) {
-				return new Bound<>(value, inclusive);
-			}
-
-			return unbounded();
+		@Override
+		public String toString() {
+			return value.map(Object::toString).orElse("unbounded");
 		}
 
 	}
@@ -521,7 +510,6 @@ public final class Range<T> {
 		 * Create a {@link Range} given the upper {@link Bound}.
 		 *
 		 * @param upper must not be {@literal null}.
-		 * @return
 		 */
 		public Range<T> to(Bound<T> upper) {
 

src/main/java/org/springframework/data/domain/ScrollPosition.java

@@ -29,7 +29,7 @@ public interface ScrollPosition {
 	/**
 	 * Returns whether the current scroll position is the initial one.
 	 *
-	 * @return
+	 * @return {@literal true} if the current scroll position is the initial one.
 	 */
 	boolean isInitial();
 
@@ -54,7 +54,7 @@ public interface ScrollPosition {
 	/**
 	 * Creates a new {@link ScrollPosition} from an {@code offset}.
 	 *
-	 * @param offset
+	 * @param offset the scroll offset.
 	 * @return a new {@link OffsetScrollPosition} with the given {@code offset}.
 	 */
 	static OffsetScrollPosition offset(long offset) {
@@ -111,4 +111,5 @@ public interface ScrollPosition {
 			return this == FORWARD ? BACKWARD : FORWARD;
 		}
 	}
+
 }

src/main/java/org/springframework/data/domain/Slice.java

@@ -54,35 +54,35 @@ public interface Slice<T> extends Streamable<T> {
 	/**
 	 * Returns the page content as {@link List}.
 	 *
-	 * @return
+	 * @return the page content as {@link List}.
 	 */
 	List<T> getContent();
 
 	/**
 	 * Returns whether the {@link Slice} has content at all.
 	 *
-	 * @return
+	 * @return {@literal true} if the {@link Slice} has content at all.
 	 */
 	boolean hasContent();
 
 	/**
 	 * Returns the sorting parameters for the {@link Slice}.
 	 *
-	 * @return
+	 * @return the sorting parameters for the {@link Slice}.
 	 */
 	Sort getSort();
 
 	/**
 	 * Returns whether the current {@link Slice} is the first one.
 	 *
-	 * @return
+	 * @return {@literal true} if the current {@link Slice} is the first one.
 	 */
 	boolean isFirst();
 
 	/**
 	 * Returns whether the current {@link Slice} is the last one.
 	 *
-	 * @return
+	 * @return {@literal true} if the current {@link Slice} is the last one.
 	 */
 	boolean isLast();
 
@@ -103,7 +103,7 @@ public interface Slice<T> extends Streamable<T> {
 	/**
 	 * Returns the {@link Pageable} that's been used to request the current {@link Slice}.
 	 *
-	 * @return
+	 * @return the {@link Pageable} that's been used to request the current {@link Slice}.
 	 * @since 2.0
 	 */
 	default Pageable getPageable() {
@@ -114,7 +114,7 @@ public interface Slice<T> extends Streamable<T> {
 	 * Returns the {@link Pageable} to request the next {@link Slice}. Can be {@link Pageable#unpaged()} in case the
 	 * current {@link Slice} is already the last one. Clients should check {@link #hasNext()} before calling this method.
 	 *
-	 * @return
+	 * @return the {@link Pageable} to request the next {@link Slice}.
 	 * @see #nextOrLastPageable()
 	 */
 	Pageable nextPageable();
@@ -124,26 +124,17 @@ public interface Slice<T> extends Streamable<T> {
 	 * current {@link Slice} is already the first one. Clients should check {@link #hasPrevious()} before calling this
 	 * method.
 	 *
-	 * @return
+	 * @return the {@link Pageable} to request the previous {@link Slice}.
 	 * @see #previousPageable()
 	 */
 	Pageable previousPageable();
 
-	/**
-	 * Returns a new {@link Slice} with the content of the current one mapped by the given {@link Converter}.
-	 *
-	 * @param converter must not be {@literal null}.
-	 * @return a new {@link Slice} with the content of the current one mapped by the given {@link Converter}.
-	 * @since 1.10
-	 */
-	@Override
-	<U> Slice<U> map(Function<? super T, ? extends U> converter);
-
 	/**
 	 * Returns the {@link Pageable} describing the next slice or the one describing the current slice in case it's the
 	 * last one.
 	 *
-	 * @return
+	 * @return the {@link Pageable} describing the next slice or the one describing the current slice in case it's the
+	 *         last one
 	 * @since 2.2
 	 */
 	default Pageable nextOrLastPageable() {
@@ -154,10 +145,22 @@ public interface Slice<T> extends Streamable<T> {
 	 * Returns the {@link Pageable} describing the previous slice or the one describing the current slice in case it's the
 	 * first one.
 	 *
-	 * @return
+	 * @return the {@link Pageable} describing the previous slice or the one describing the current slice in case it's the
+	 *         first one.
 	 * @since 2.2
 	 */
 	default Pageable previousOrFirstPageable() {
 		return hasPrevious() ? previousPageable() : getPageable();
 	}
+
+	/**
+	 * Returns a new {@link Slice} with the content of the current one mapped by the given {@link Converter}.
+	 *
+	 * @param converter must not be {@literal null}.
+	 * @return a new {@link Slice} with the content of the current one mapped by the given {@link Converter}.
+	 * @since 1.10
+	 */
+	@Override
+	<U> Slice<U> map(Function<? super T, ? extends U> converter);
+
 }

src/main/java/org/springframework/data/domain/SliceImpl.java

@@ -30,8 +30,7 @@ import org.springframework.lang.Nullable;
  */
 public class SliceImpl<T> extends Chunk<T> {
 
-	@Serial
-	private static final long serialVersionUID = 867755909294344406L;
+	private static final @Serial long serialVersionUID = 867755909294344406L;
 
 	private final boolean hasNext;
 	private final Pageable pageable;
@@ -71,19 +70,6 @@ public class SliceImpl<T> extends Chunk<T> {
 		return new SliceImpl<>(getConvertedContent(converter), pageable, hasNext);
 	}
 
-	@Override
-	public String toString() {
-
-		String contentType = "UNKNOWN";
-		List<T> content = getContent();
-
-		if (!content.isEmpty()) {
-			contentType = content.get(0).getClass().getName();
-		}
-
-		return String.format("Slice %d containing %s instances", getNumber(), contentType);
-	}
-
 	@Override
 	public boolean equals(@Nullable Object obj) {
 
@@ -100,12 +86,20 @@ public class SliceImpl<T> extends Chunk<T> {
 
 	@Override
 	public int hashCode() {
+		return 31 * super.hashCode() + (hasNext ? 1 : 0);
+	}
+
+	@Override
+	public String toString() {
 
-		int result = 17;
+		String contentType = "UNKNOWN";
+		List<T> content = getContent();
 
-		result += 31 * (hasNext ? 1 : 0);
-		result += 31 * super.hashCode();
+		if (!content.isEmpty()) {
+			contentType = content.get(0).getClass().getName();
+		}
 
-		return result;
+		return String.format("Slice %d containing %s instances", getNumber(), contentType);
 	}
+
 }

src/main/java/org/springframework/data/domain/Sort.java

@@ -30,6 +30,8 @@ import java.util.stream.Collectors;
 import org.springframework.data.util.MethodInvocationRecorder;
 import org.springframework.data.util.MethodInvocationRecorder.Recorded;
 import org.springframework.data.util.Streamable;
+import org.springframework.lang.CheckReturnValue;
+import org.springframework.lang.Contract;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
@@ -160,6 +162,7 @@ public class Sort implements Streamable<org.springframework.data.domain.Sort.Ord
 	 *
 	 * @return a new {@link Sort} with the current setup but descending order direction.
 	 */
+	@Contract("-> new")
 	public Sort descending() {
 		return withDirection(Direction.DESC);
 	}
@@ -169,6 +172,7 @@ public class Sort implements Streamable<org.springframework.data.domain.Sort.Ord
 	 *
 	 * @return a new {@link Sort} with the current setup but ascending order direction.
 	 */
+	@Contract("-> new")
 	public Sort ascending() {
 		return withDirection(Direction.ASC);
 	}
@@ -200,6 +204,8 @@ public class Sort implements Streamable<org.springframework.data.domain.Sort.Ord
 	 * @return a new {@link Sort} consisting of the {@link Order}s of the current {@link Sort} combined with the given
 	 *         ones.
 	 */
+	@Contract("_ -> new")
+	@CheckReturnValue
 	public Sort and(Sort sort) {
 
 		Assert.notNull(sort, "Sort must not be null");
@@ -220,6 +226,7 @@ public class Sort implements Streamable<org.springframework.data.domain.Sort.Ord
 	 * @return a new {@link Sort} object with reversed sort orders applied.
 	 * @since 3.1
 	 */
+	@Contract("-> new")
 	public Sort reverse() {
 
 		List<Order> reversed = doReverse();
@@ -277,10 +284,7 @@ public class Sort implements Streamable<org.springframework.data.domain.Sort.Ord
 
 	@Override
 	public int hashCode() {
-
-		int result = 17;
-		result = 31 * result + orders.hashCode();
-		return result;
+		return orders.hashCode();
 	}
 
 	@Override
@@ -381,14 +385,14 @@ public class Sort implements Streamable<org.springframework.data.domain.Sort.Ord
 		NATIVE,
 
 		/**
-		 * A hint to the used data store to order entries with null values before non null entries.
+		 * A hint to the used data store to order entries with null values before non-null entries.
 		 */
 		NULLS_FIRST,
 
 		/**
-		 * A hint to the used data store to order entries with null values after non null entries.
+		 * A hint to the used data store to order entries with null values after non-null entries.
 		 */
-		NULLS_LAST;
+		NULLS_LAST
 	}
 
 	/**
@@ -541,6 +545,8 @@ public class Sort implements Streamable<org.springframework.data.domain.Sort.Ord
 		 * @param direction the new direction to use.
 		 * @return a new {@link Order} with the given {@link Direction} applied.
 		 */
+		@Contract("_ -> new")
+		@CheckReturnValue
 		public Order with(Direction direction) {
 			return new Order(direction, this.property, this.ignoreCase, this.nullHandling);
 		}
@@ -551,6 +557,7 @@ public class Sort implements Streamable<org.springframework.data.domain.Sort.Ord
 		 * @return a reversed {@link Order} with the given {@link Direction} applied.
 		 * @since 3.1
 		 */
+		@Contract("-> new")
 		public Order reverse() {
 			return with(this.direction == Direction.ASC ? Direction.DESC : Direction.ASC);
 		}
@@ -562,6 +569,8 @@ public class Sort implements Streamable<org.springframework.data.domain.Sort.Ord
 		 * @return a new {@link Order} with the {@code property} name applied.
 		 * @since 1.13
 		 */
+		@Contract("_ -> new")
+		@CheckReturnValue
 		public Order withProperty(String property) {
 			return new Order(this.direction, property, this.ignoreCase, this.nullHandling);
 		}
@@ -572,6 +581,8 @@ public class Sort implements Streamable<org.springframework.data.domain.Sort.Ord
 		 * @param properties properties to sort by.
 		 * @return a new {@link Sort} instance for the given properties using {@link #getDirection()}.
 		 */
+		@Contract("_ -> new")
+		@CheckReturnValue
 		public Sort withProperties(String... properties) {
 			return Sort.by(this.direction, properties);
 		}
@@ -592,6 +603,8 @@ public class Sort implements Streamable<org.springframework.data.domain.Sort.Ord
 		 * @return a new {@link Order} with the given {@link NullHandling} applied.
 		 * @since 1.8
 		 */
+		@Contract("_ -> new")
+		@CheckReturnValue
 		public Order with(NullHandling nullHandling) {
 			return new Order(direction, this.property, ignoreCase, nullHandling);
 		}
@@ -602,6 +615,7 @@ public class Sort implements Streamable<org.springframework.data.domain.Sort.Ord
 		 * @return a new {@link Order} with {@link NullHandling#NULLS_FIRST} as null handling hint applied.
 		 * @since 1.8
 		 */
+		@Contract("-> new")
 		public Order nullsFirst() {
 			return with(NullHandling.NULLS_FIRST);
 		}
@@ -612,6 +626,7 @@ public class Sort implements Streamable<org.springframework.data.domain.Sort.Ord
 		 * @return a new {@link Order} with {@link NullHandling#NULLS_LAST} as null handling hint applied.
 		 * @since 1.7
 		 */
+		@Contract("-> new")
 		public Order nullsLast() {
 			return with(NullHandling.NULLS_LAST);
 		}
@@ -622,6 +637,7 @@ public class Sort implements Streamable<org.springframework.data.domain.Sort.Ord
 		 * @return a new {@link Order} with {@link NullHandling#NATIVE} as null handling hint applied.
 		 * @since 1.7
 		 */
+		@Contract("-> new")
 		public Order nullsNative() {
 			return with(NullHandling.NATIVE);
 		}
@@ -636,19 +652,6 @@ public class Sort implements Streamable<org.springframework.data.domain.Sort.Ord
 			return nullHandling;
 		}
 
-		@Override
-		public int hashCode() {
-
-			int result = 17;
-
-			result = 31 * result + direction.hashCode();
-			result = 31 * result + property.hashCode();
-			result = 31 * result + (ignoreCase ? 1 : 0);
-			result = 31 * result + nullHandling.hashCode();
-
-			return result;
-		}
-
 		@Override
 		public boolean equals(@Nullable Object obj) {
 
@@ -664,6 +667,11 @@ public class Sort implements Streamable<org.springframework.data.domain.Sort.Ord
 					&& this.ignoreCase == that.ignoreCase && this.nullHandling.equals(that.nullHandling);
 		}
 
+		@Override
+		public int hashCode() {
+			return ObjectUtils.nullSafeHash(direction, property, ignoreCase, nullHandling);
+		}
+
 		@Override
 		public String toString() {
 
@@ -679,6 +687,7 @@ public class Sort implements Streamable<org.springframework.data.domain.Sort.Ord
 
 			return result;
 		}
+
 	}
 
 	/**

src/main/java/org/springframework/data/domain/TypedExample.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.data.domain;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 
@@ -49,7 +50,7 @@ class TypedExample<T> implements Example<T> {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 
 		if (this == o) {
 			return true;
@@ -68,9 +69,7 @@ class TypedExample<T> implements Example<T> {
 
 	@Override
 	public int hashCode() {
-		int result = ObjectUtils.nullSafeHashCode(probe);
-		result = 31 * result + ObjectUtils.nullSafeHashCode(matcher);
-		return result;
+		return ObjectUtils.nullSafeHash(probe, matcher);
 	}
 
 	@Override

src/main/java/org/springframework/data/domain/TypedExampleMatcher.java

@@ -20,6 +20,7 @@ import java.util.Collections;
 import java.util.LinkedHashSet;
 import java.util.Set;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 
@@ -193,8 +194,9 @@ class TypedExampleMatcher implements ExampleMatcher {
 		return new PropertySpecifier(propertyPath);
 	}
 
+
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 
 		if (this == o) {
 			return true;
@@ -217,7 +219,6 @@ class TypedExampleMatcher implements ExampleMatcher {
 		}
 
 		if (!ObjectUtils.nullSafeEquals(propertySpecifiers, that.propertySpecifiers)) {
-
 			return false;
 		}
 
@@ -230,13 +231,8 @@ class TypedExampleMatcher implements ExampleMatcher {
 
 	@Override
 	public int hashCode() {
-		int result = ObjectUtils.nullSafeHashCode(nullHandler);
-		result = 31 * result + ObjectUtils.nullSafeHashCode(defaultStringMatcher);
-		result = 31 * result + ObjectUtils.nullSafeHashCode(propertySpecifiers);
-		result = 31 * result + ObjectUtils.nullSafeHashCode(ignoredPaths);
-		result = 31 * result + (defaultIgnoreCase ? 1 : 0);
-		result = 31 * result + ObjectUtils.nullSafeHashCode(mode);
-		return result;
+		return ObjectUtils.nullSafeHash(nullHandler, defaultStringMatcher, propertySpecifiers, ignoredPaths,
+				defaultIgnoreCase, mode);
 	}
 
 	@Override

src/main/java/org/springframework/data/domain/Unpaged.java

@@ -15,6 +15,8 @@
  */
 package org.springframework.data.domain;
 
+import org.springframework.lang.Nullable;
+
 /**
  * {@link Pageable} implementation to represent the absence of pagination information.
  *
@@ -91,7 +93,7 @@ final class Unpaged implements Pageable {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 		if (this == o) {
 			return true;
 		}

src/main/java/org/springframework/data/domain/Window.java

@@ -41,7 +41,6 @@ public interface Window<T> extends Streamable<T> {
 	 * @param items the list of data.
 	 * @param positionFunction the list of data.
 	 * @return the {@link Window}.
-	 * @param <T>
 	 */
 	static <T> Window<T> from(List<T> items, IntFunction<? extends ScrollPosition> positionFunction) {
 		return new WindowImpl<>(items, positionFunction, false);
@@ -54,7 +53,6 @@ public interface Window<T> extends Streamable<T> {
 	 * @param positionFunction the list of data.
 	 * @param hasNext
 	 * @return the {@link Window}.
-	 * @param <T>
 	 */
 	static <T> Window<T> from(List<T> items, IntFunction<? extends ScrollPosition> positionFunction, boolean hasNext) {
 		return new WindowImpl<>(items, positionFunction, hasNext);
@@ -78,14 +76,14 @@ public interface Window<T> extends Streamable<T> {
 	/**
 	 * Returns the windows content as {@link List}.
 	 *
-	 * @return
+	 * @return the windows content as {@link List}.
 	 */
 	List<T> getContent();
 
 	/**
 	 * Returns whether the current window is the last one.
 	 *
-	 * @return
+	 * @return {@literal true} if the current window is the last one.
 	 */
 	default boolean isLast() {
 		return !hasNext();
@@ -101,13 +99,14 @@ public interface Window<T> extends Streamable<T> {
 	/**
 	 * Returns whether the underlying scroll mechanism can provide a {@link ScrollPosition} at {@code index}.
 	 *
-	 * @param index
+	 * @param index the result index to check for a {@link ScrollPosition}.
 	 * @return {@code true} if a {@link ScrollPosition} can be created; {@code false} otherwise.
 	 * @see #positionAt(int)
 	 */
 	default boolean hasPosition(int index) {
 		try {
-			return positionAt(index) != null;
+			positionAt(index);
+			return true;
 		} catch (IllegalStateException e) {
 			return false;
 		}
@@ -116,8 +115,8 @@ public interface Window<T> extends Streamable<T> {
 	/**
 	 * Returns the {@link ScrollPosition} at {@code index}.
 	 *
-	 * @param index
-	 * @return
+	 * @param index index of the window element to determine the scroll position for.
+	 * @return the scroll position for the given object index.
 	 * @throws IndexOutOfBoundsException if the index is out of range ({@code index < 0 || index >= size()}).
 	 * @throws IllegalStateException if the underlying scroll mechanism cannot provide a scroll position for the given
 	 *           object.
@@ -127,8 +126,8 @@ public interface Window<T> extends Streamable<T> {
 	/**
 	 * Returns the {@link ScrollPosition} for {@code object}.
 	 *
-	 * @param object
-	 * @return
+	 * @param object member of the window to determine the scroll position for.
+	 * @return the scroll position for the given object.
 	 * @throws NoSuchElementException if the object is not part of the result.
 	 * @throws IllegalStateException if the underlying scroll mechanism cannot provide a scroll position for the given
 	 *           object.

src/main/java/org/springframework/data/domain/WindowImpl.java

@@ -22,6 +22,8 @@ import java.util.function.IntFunction;
 import java.util.stream.Collectors;
 
 import org.jetbrains.annotations.NotNull;
+
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 
@@ -86,19 +88,23 @@ class WindowImpl<T> implements Window<T> {
 		return new WindowImpl<>(stream().map(converter).collect(Collectors.toList()), positionFunction, hasNext);
 	}
 
-	@NotNull
 	@Override
 	public Iterator<T> iterator() {
 		return items.iterator();
 	}
 
 	@Override
-	public boolean equals(Object o) {
-		if (this == o)
+	public boolean equals(@Nullable Object o) {
+
+		if (this == o) {
 			return true;
-		if (o == null || getClass() != o.getClass())
+		}
+		if (o == null || getClass() != o.getClass()) {
 			return false;
+		}
+
 		WindowImpl<?> that = (WindowImpl<?>) o;
+
 		return ObjectUtils.nullSafeEquals(items, that.items)
 				&& ObjectUtils.nullSafeEquals(positionFunction, that.positionFunction)
 				&& ObjectUtils.nullSafeEquals(hasNext, that.hasNext);
@@ -106,9 +112,11 @@ class WindowImpl<T> implements Window<T> {
 
 	@Override
 	public int hashCode() {
+
 		int result = ObjectUtils.nullSafeHashCode(items);
 		result = 31 * result + ObjectUtils.nullSafeHashCode(positionFunction);
 		result = 31 * result + ObjectUtils.nullSafeHashCode(hasNext);
+
 		return result;
 	}
 

src/main/java/org/springframework/data/domain/jaxb/OrderAdapter.java

@@ -20,6 +20,7 @@ import jakarta.xml.bind.annotation.adapters.XmlAdapter;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.domain.Sort.Order;
 import org.springframework.data.domain.jaxb.SpringDataJaxb.OrderDto;
+import org.springframework.lang.Contract;
 import org.springframework.lang.Nullable;
 
 /**
@@ -46,6 +47,7 @@ public class OrderAdapter extends XmlAdapter<OrderDto, Order> {
 	}
 
 	@Nullable
+	@Contract("null -> null")
 	@Override
 	public Order unmarshal(@Nullable OrderDto source) {
 

src/main/java/org/springframework/data/domain/jaxb/PageAdapter.java

@@ -23,6 +23,7 @@ import java.util.List;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.jaxb.SpringDataJaxb.PageDto;
 import org.springframework.hateoas.Link;
+import org.springframework.lang.Contract;
 import org.springframework.lang.Nullable;
 
 /**
@@ -33,6 +34,7 @@ import org.springframework.lang.Nullable;
 public class PageAdapter extends XmlAdapter<PageDto, Page<Object>> {
 
 	@Nullable
+	@Contract("null -> null; !null -> !null")
 	@Override
 	public PageDto marshal(@Nullable Page<Object> source) {
 
@@ -48,6 +50,7 @@ public class PageAdapter extends XmlAdapter<PageDto, Page<Object>> {
 	}
 
 	@Nullable
+	@Contract("_ -> null")
 	@Override
 	public Page<Object> unmarshal(@Nullable PageDto v) {
 		return null;

src/main/java/org/springframework/data/domain/jaxb/SortAdapter.java

@@ -19,6 +19,7 @@ import jakarta.xml.bind.annotation.adapters.XmlAdapter;
 
 import org.springframework.data.domain.Sort;
 import org.springframework.data.domain.jaxb.SpringDataJaxb.SortDto;
+import org.springframework.lang.Contract;
 import org.springframework.lang.NonNull;
 import org.springframework.lang.Nullable;
 
@@ -32,6 +33,7 @@ public class SortAdapter extends XmlAdapter<SortDto, Sort> {
 	public static final SortAdapter INSTANCE = new SortAdapter();
 
 	@Nullable
+	@Contract("null -> null; !null -> !null")
 	@Override
 	public SortDto marshal(@Nullable Sort source) {
 

src/main/java/org/springframework/data/domain/jaxb/SpringDataJaxb.java

@@ -109,7 +109,7 @@ public abstract class SpringDataJaxb {
 	 * @param adapter must not be {@literal null}.
 	 * @return
 	 */
-	public static <T, S> List<T> unmarshal(Collection<S> source, XmlAdapter<S, T> adapter) {
+	public static <T, S> List<T> unmarshal(@Nullable Collection<S> source, XmlAdapter<S, T> adapter) {
 
 		Assert.notNull(adapter, "Adapter must not be null");
 

src/main/java/org/springframework/data/geo/Box.java

@@ -15,8 +15,11 @@
  */
 package org.springframework.data.geo;
 
+import java.io.Serial;
+
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.ObjectUtils;
 
 /**
  * Represents a geospatial box value
@@ -28,7 +31,7 @@ import org.springframework.util.Assert;
  */
 public class Box implements Shape {
 
-	private static final long serialVersionUID = 8198095179084040711L;
+	private static final @Serial long serialVersionUID = 8198095179084040711L;
 
 	private final Point first;
 	private final Point second;
@@ -66,7 +69,7 @@ public class Box implements Shape {
 	/**
 	 * Returns the first {@link Point} making up the {@link Box}.
 	 *
-	 * @return
+	 * @return the first {@link Point} making up the {@link Box}.
 	 */
 	public Point getFirst() {
 		return first;
@@ -75,26 +78,15 @@ public class Box implements Shape {
 	/**
 	 * Returns the second {@link Point} making up the {@link Box}.
 	 *
-	 * @return
+	 * @return the second {@link Point} making up the {@link Box}.
 	 */
 	public Point getSecond() {
 		return second;
 	}
 
-	@Override
-	public String toString() {
-		return String.format("Box [%s, %s]", first, second);
-	}
-
 	@Override
 	public int hashCode() {
-
-		int result = 31;
-
-		result += 17 * first.hashCode();
-		result += 17 * second.hashCode();
-
-		return result;
+		return ObjectUtils.nullSafeHash(first, second);
 	}
 
 	@Override
@@ -110,4 +102,9 @@ public class Box implements Shape {
 
 		return this.first.equals(that.first) && this.second.equals(that.second);
 	}
+
+	@Override
+	public String toString() {
+		return String.format("Box [%s, %s]", first, second);
+	}
 }

src/main/java/org/springframework/data/geo/Circle.java

@@ -15,7 +15,10 @@
  */
 package org.springframework.data.geo;
 
-import org.springframework.data.annotation.PersistenceConstructor;
+import java.io.Serial;
+
+import org.springframework.data.annotation.PersistenceCreator;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 
@@ -29,7 +32,7 @@ import org.springframework.util.ObjectUtils;
  */
 public class Circle implements Shape {
 
-	private static final long serialVersionUID = 5215611530535947924L;
+	private static final @Serial long serialVersionUID = 5215611530535947924L;
 
 	private final Point center;
 	private final Distance radius;
@@ -40,7 +43,7 @@ public class Circle implements Shape {
 	 * @param center must not be {@literal null}.
 	 * @param radius must not be {@literal null} and it's value greater or equal to zero.
 	 */
-	@PersistenceConstructor
+	@PersistenceCreator
 	public Circle(Point center, Distance radius) {
 
 		Assert.notNull(center, "Center point must not be null");
@@ -65,8 +68,8 @@ public class Circle implements Shape {
 	 * Creates a new {@link Circle} from the given coordinates and radius as {@link Distance} with a
 	 * {@link Metrics#NEUTRAL}.
 	 *
-	 * @param centerX
-	 * @param centerY
+	 * @param centerX X coordinate of the center point.
+	 * @param centerY Y coordinate of the center point.
 	 * @param radius must be greater or equal to zero.
 	 */
 	public Circle(double centerX, double centerY, double radius) {
@@ -85,14 +88,14 @@ public class Circle implements Shape {
 	/**
 	 * Returns the radius of the {@link Circle}.
 	 *
-	 * @return
+	 * @return the radius.
 	 */
 	public Distance getRadius() {
 		return radius;
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 
 		if (this == o) {
 			return true;
@@ -111,9 +114,7 @@ public class Circle implements Shape {
 
 	@Override
 	public int hashCode() {
-		int result = ObjectUtils.nullSafeHashCode(center);
-		result = 31 * result + ObjectUtils.nullSafeHashCode(radius);
-		return result;
+		return ObjectUtils.nullSafeHash(center, radius);
 	}
 
 	@Override

src/main/java/org/springframework/data/geo/CustomMetric.java

@@ -15,6 +15,8 @@
  */
 package org.springframework.data.geo;
 
+import java.io.Serial;
+
 import org.springframework.util.Assert;
 
 /**
@@ -26,7 +28,7 @@ import org.springframework.util.Assert;
  */
 public class CustomMetric implements Metric {
 
-	private static final long serialVersionUID = -2972074177454114228L;
+	private static final @Serial long serialVersionUID = -2972074177454114228L;
 
 	private final double multiplier;
 	private final String abbreviation;
@@ -34,7 +36,7 @@ public class CustomMetric implements Metric {
 	/**
 	 * Creates a custom {@link Metric} using the given multiplier.
 	 *
-	 * @param multiplier
+	 * @param multiplier metric multiplier.
 	 */
 	public CustomMetric(double multiplier) {
 
@@ -44,7 +46,7 @@ public class CustomMetric implements Metric {
 	/**
 	 * Creates a custom {@link Metric} using the given multiplier and abbreviation.
 	 *
-	 * @param multiplier
+	 * @param multiplier metric multiplier.
 	 * @param abbreviation must not be {@literal null}.
 	 */
 	public CustomMetric(double multiplier, String abbreviation) {

src/main/java/org/springframework/data/geo/Distance.java

@@ -15,10 +15,13 @@
  */
 package org.springframework.data.geo;
 
+import java.io.Serial;
 import java.io.Serializable;
 
 import org.springframework.data.domain.Range;
 import org.springframework.data.domain.Range.Bound;
+import org.springframework.lang.CheckReturnValue;
+import org.springframework.lang.Contract;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
@@ -32,7 +35,7 @@ import org.springframework.util.ObjectUtils;
  */
 public final class Distance implements Serializable, Comparable<Distance> {
 
-	private static final long serialVersionUID = 2460886201934027744L;
+	private static final @Serial long serialVersionUID = 2460886201934027744L;
 
 	/**
 	 * The distance value in the current {@link Metric}.
@@ -47,7 +50,7 @@ public final class Distance implements Serializable, Comparable<Distance> {
 	/**
 	 * Creates a new {@link Distance} with a neutral metric. This means the provided value needs to be in normalized form.
 	 *
-	 * @param value
+	 * @param value distance value.
 	 */
 	public Distance(double value) {
 		this(value, Metrics.NEUTRAL);
@@ -81,11 +84,11 @@ public final class Distance implements Serializable, Comparable<Distance> {
 	/**
 	 * Creates a new {@link Range} by creating minimum and maximum {@link Distance} from the given values.
 	 *
-	 * @param minValue
+	 * @param minValue minimum value.
 	 * @param minMetric can be {@literal null}.
-	 * @param maxValue
+	 * @param maxValue maximum value.
 	 * @param maxMetric can be {@literal null}.
-	 * @return
+	 * @return the {@link Range} between the given values.
 	 */
 	public static Range<Distance> between(double minValue, Metric minMetric, double maxValue, Metric maxMetric) {
 		return between(new Distance(minValue, minMetric), new Distance(maxValue, maxMetric));
@@ -94,7 +97,7 @@ public final class Distance implements Serializable, Comparable<Distance> {
 	/**
 	 * Returns the normalized value regarding the underlying {@link Metric}.
 	 *
-	 * @return
+	 * @return the normalized value.
 	 */
 	public double getNormalizedValue() {
 		return value / metric.getMultiplier();
@@ -115,8 +118,10 @@ public final class Distance implements Serializable, Comparable<Distance> {
 	 * current one.
 	 *
 	 * @param other must not be {@literal null}.
-	 * @return
+	 * @return sum of this and the other distance.
 	 */
+	@Contract("_ -> new")
+	@CheckReturnValue
 	public Distance add(Distance other) {
 
 		Assert.notNull(other, "Distance to add must not be null");
@@ -131,8 +136,9 @@ public final class Distance implements Serializable, Comparable<Distance> {
 	 *
 	 * @param other must not be {@literal null}.
 	 * @param metric must not be {@literal null}.
-	 * @return
+	 * @return sum of this and the other distance.
 	 */
+	@Contract("_, _ -> new")
 	public Distance add(Distance other, Metric metric) {
 
 		Assert.notNull(other, "Distance to must not be null");
@@ -149,8 +155,10 @@ public final class Distance implements Serializable, Comparable<Distance> {
 	 * same normalized value as the original instance.
 	 *
 	 * @param metric must not be {@literal null}.
-	 * @return
+	 * @return the converted {@link Distance}.
 	 */
+	@Contract("_ -> new")
+	@CheckReturnValue
 	public Distance in(Metric metric) {
 
 		Assert.notNull(metric, "Metric must not be null");
@@ -170,19 +178,6 @@ public final class Distance implements Serializable, Comparable<Distance> {
 		return difference == 0 ? 0 : difference > 0 ? 1 : -1;
 	}
 
-	@Override
-	public String toString() {
-
-		StringBuilder builder = new StringBuilder();
-		builder.append(value);
-
-		if (metric != Metrics.NEUTRAL) {
-			builder.append(" ").append(metric.toString());
-		}
-
-		return builder.toString();
-	}
-
 	public double getValue() {
 		return this.value;
 	}
@@ -192,7 +187,7 @@ public final class Distance implements Serializable, Comparable<Distance> {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 
 		if (this == o) {
 			return true;
@@ -205,16 +200,25 @@ public final class Distance implements Serializable, Comparable<Distance> {
 		if (value != distance.value) {
 			return false;
 		}
+
 		return ObjectUtils.nullSafeEquals(metric, distance.metric);
 	}
 
 	@Override
 	public int hashCode() {
-		int result;
-		long temp;
-		temp = Double.doubleToLongBits(value);
-		result = (int) (temp ^ (temp >>> 32));
-		result = 31 * result + ObjectUtils.nullSafeHashCode(metric);
-		return result;
+		return ObjectUtils.nullSafeHash(value, metric);
+	}
+
+	@Override
+	public String toString() {
+
+		StringBuilder builder = new StringBuilder();
+		builder.append(value);
+
+		if (metric != Metrics.NEUTRAL) {
+			builder.append(" ").append(metric.toString());
+		}
+
+		return builder.toString();
 	}
 }

src/main/java/org/springframework/data/geo/GeoModule.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.data.geo;
 
+import java.io.Serial;
 import java.util.List;
 
 import com.fasterxml.jackson.annotation.JsonIgnore;
@@ -30,9 +31,10 @@ import com.fasterxml.jackson.databind.module.SimpleModule;
  * @author Oliver Gierke
  * @since 1.8
  */
+@SuppressWarnings("unused")
 public class GeoModule extends SimpleModule {
 
-	private static final long serialVersionUID = 1L;
+	private static final @Serial long serialVersionUID = 1L;
 
 	/**
 	 * Creates a new {@link GeoModule} registering mixins for common geo-spatial types.

src/main/java/org/springframework/data/geo/GeoPage.java

@@ -15,6 +15,8 @@
  */
 package org.springframework.data.geo;
 
+import java.io.Serial;
+
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.PageImpl;
 import org.springframework.data.domain.Pageable;
@@ -31,7 +33,7 @@ import org.springframework.util.ObjectUtils;
  */
 public class GeoPage<T> extends PageImpl<GeoResult<T>> {
 
-	private static final long serialVersionUID = -5655267379242128600L;
+	private static final @Serial long serialVersionUID = -5655267379242128600L;
 
 	/**
 	 * The average distance of the underlying results.
@@ -55,7 +57,7 @@ public class GeoPage<T> extends PageImpl<GeoResult<T>> {
 	 *
 	 * @param results must not be {@literal null}.
 	 * @param pageable must not be {@literal null}.
-	 * @param total
+	 * @param total total number of results.
 	 */
 	public GeoPage(GeoResults<T> results, Pageable pageable, long total) {
 
@@ -64,6 +66,10 @@ public class GeoPage<T> extends PageImpl<GeoResult<T>> {
 		this.averageDistance = results.getAverageDistance();
 	}
 
+	public Distance getAverageDistance() {
+		return this.averageDistance;
+	}
+
 	@Override
 	public boolean equals(@Nullable Object obj) {
 
@@ -82,8 +88,4 @@ public class GeoPage<T> extends PageImpl<GeoResult<T>> {
 	public int hashCode() {
 		return super.hashCode() + ObjectUtils.nullSafeHashCode(this.averageDistance);
 	}
-
-	public Distance getAverageDistance() {
-		return this.averageDistance;
-	}
 }

src/main/java/org/springframework/data/geo/GeoResult.java

@@ -15,8 +15,10 @@
  */
 package org.springframework.data.geo;
 
+import java.io.Serial;
 import java.io.Serializable;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 
@@ -29,7 +31,7 @@ import org.springframework.util.ObjectUtils;
  */
 public final class GeoResult<T> implements Serializable {
 
-	private static final long serialVersionUID = 1637452570977581370L;
+	private static final @Serial long serialVersionUID = 1637452570977581370L;
 
 	private final T content;
 	private final Distance distance;
@@ -52,7 +54,7 @@ public final class GeoResult<T> implements Serializable {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 
 		if (this == o) {
 			return true;
@@ -71,9 +73,7 @@ public final class GeoResult<T> implements Serializable {
 
 	@Override
 	public int hashCode() {
-		int result = ObjectUtils.nullSafeHashCode(content);
-		result = 31 * result + ObjectUtils.nullSafeHashCode(distance);
-		return result;
+		return ObjectUtils.nullSafeHash(content, distance);
 	}
 
 	@Override

src/main/java/org/springframework/data/geo/GeoResults.java

@@ -16,12 +16,14 @@
 package org.springframework.data.geo;
 
 
+import java.io.Serial;
 import java.io.Serializable;
 import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 
-import org.springframework.data.annotation.PersistenceConstructor;
+import org.springframework.data.annotation.PersistenceCreator;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
@@ -35,7 +37,7 @@ import org.springframework.util.StringUtils;
  */
 public class GeoResults<T> implements Iterable<GeoResult<T>>, Serializable {
 
-	private static final long serialVersionUID = 8347363491300219485L;
+	private static final @Serial long serialVersionUID = 8347363491300219485L;
 
 	private final List<? extends GeoResult<T>> results;
 	private final Distance averageDistance;
@@ -67,7 +69,7 @@ public class GeoResults<T> implements Iterable<GeoResult<T>>, Serializable {
 	 * @param results must not be {@literal null}.
 	 * @param averageDistance must not be {@literal null}.
 	 */
-	@PersistenceConstructor
+	@PersistenceCreator
 	public GeoResults(List<? extends GeoResult<T>> results, Distance averageDistance) {
 
 		Assert.notNull(results, "Results must not be null");
@@ -89,19 +91,20 @@ public class GeoResults<T> implements Iterable<GeoResult<T>>, Serializable {
 	/**
 	 * Returns the actual content of the {@link GeoResults}.
 	 *
-	 * @return
+	 * @return the actual content.
 	 */
 	public List<GeoResult<T>> getContent() {
 		return Collections.unmodifiableList(results);
 	}
 
+	@Override
 	@SuppressWarnings("unchecked")
 	public Iterator<GeoResult<T>> iterator() {
 		return (Iterator<GeoResult<T>>) results.iterator();
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 
 		if (this == o) {
 			return true;
@@ -120,9 +123,7 @@ public class GeoResults<T> implements Iterable<GeoResult<T>>, Serializable {
 
 	@Override
 	public int hashCode() {
-		int result = ObjectUtils.nullSafeHashCode(results);
-		result = 31 * result + ObjectUtils.nullSafeHashCode(averageDistance);
-		return result;
+		return ObjectUtils.nullSafeHash(results, averageDistance);
 	}
 
 	@Override

src/main/java/org/springframework/data/geo/Point.java

@@ -15,12 +15,14 @@
  */
 package org.springframework.data.geo;
 
+import java.io.Serial;
 import java.io.Serializable;
 import java.util.Locale;
 
-import org.springframework.data.annotation.PersistenceConstructor;
+import org.springframework.data.annotation.PersistenceCreator;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.ObjectUtils;
 
 /**
  * Represents a geospatial point value.
@@ -32,7 +34,7 @@ import org.springframework.util.Assert;
  */
 public class Point implements Serializable {
 
-	private static final long serialVersionUID = 3583151228933783558L;
+	private static final @Serial long serialVersionUID = 3583151228933783558L;
 
 	private final double x;
 	private final double y;
@@ -40,10 +42,10 @@ public class Point implements Serializable {
 	/**
 	 * Creates a {@link Point} from the given {@code x}, {@code y} coordinate.
 	 *
-	 * @param x
-	 * @param y
+	 * @param x x coordinate.
+	 * @param y y coordinate.
 	 */
-	@PersistenceConstructor
+	@PersistenceCreator
 	public Point(double x, double y) {
 		this.x = x;
 		this.y = y;
@@ -65,7 +67,7 @@ public class Point implements Serializable {
 	/**
 	 * Returns the x-coordinate of the {@link Point}.
 	 *
-	 * @return
+	 * @return the x-coordinate of the {@link Point}.
 	 */
 	public double getX() {
 		return x;
@@ -74,7 +76,7 @@ public class Point implements Serializable {
 	/**
 	 * Returns the y-coordinate of the {@link Point}.
 	 *
-	 * @return
+	 * @return the y-coordinate of the {@link Point}.
 	 */
 	public double getY() {
 		return y;
@@ -82,16 +84,7 @@ public class Point implements Serializable {
 
 	@Override
 	public int hashCode() {
-
-		int result = 1;
-
-		long temp = Double.doubleToLongBits(x);
-		result = 31 * result + (int) (temp ^ temp >>> 32);
-
-		temp = Double.doubleToLongBits(y);
-		result = 31 * result + (int) (temp ^ temp >>> 32);
-
-		return result;
+		return ObjectUtils.nullSafeHash(x, y);
 	}
 
 	@Override

src/main/java/org/springframework/data/geo/Polygon.java

@@ -16,13 +16,15 @@
 package org.springframework.data.geo;
 
 
+import java.io.Serial;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 
-import org.springframework.data.annotation.PersistenceConstructor;
+import org.springframework.data.annotation.PersistenceCreator;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
@@ -36,7 +38,7 @@ import org.springframework.util.StringUtils;
  */
 public class Polygon implements Iterable<Point>, Shape {
 
-	private static final long serialVersionUID = -2705040068154648988L;
+	private static final @Serial long serialVersionUID = -2705040068154648988L;
 
 	private final List<Point> points;
 
@@ -46,7 +48,7 @@ public class Polygon implements Iterable<Point>, Shape {
 	 * @param x must not be {@literal null}.
 	 * @param y must not be {@literal null}.
 	 * @param z must not be {@literal null}.
-	 * @param others
+	 * @param others other points.
 	 */
 	public Polygon(Point x, Point y, Point z, Point... others) {
 
@@ -67,7 +69,7 @@ public class Polygon implements Iterable<Point>, Shape {
 	 *
 	 * @param points must not be {@literal null}.
 	 */
-	@PersistenceConstructor
+	@PersistenceCreator
 	public Polygon(List<? extends Point> points) {
 
 		Assert.notNull(points, "Points must not be null");
@@ -92,12 +94,13 @@ public class Polygon implements Iterable<Point>, Shape {
 		return this.points;
 	}
 
+	@Override
 	public Iterator<Point> iterator() {
 		return this.points.iterator();
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 
 		if (this == o) {
 			return true;

src/main/java/org/springframework/data/geo/format/DistanceFormatter.java

@@ -27,6 +27,7 @@ import org.springframework.data.geo.Distance;
 import org.springframework.data.geo.Metric;
 import org.springframework.data.geo.Metrics;
 import org.springframework.format.Formatter;
+import org.springframework.lang.Contract;
 import org.springframework.lang.Nullable;
 import org.springframework.util.StringUtils;
 
@@ -57,15 +58,17 @@ public enum DistanceFormatter implements Converter<String, Distance>, Formatter<
 		SUPPORTED_METRICS = Collections.unmodifiableMap(metrics);
 	}
 
+	@Contract("null -> null; !null -> !null")
 	@Nullable
 	@Override
-	public final Distance convert(String source) {
+	public final Distance convert(@Nullable String source) {
 		return source == null ? null : doConvert(source.trim().toLowerCase(Locale.US));
 	}
 
 	@Override
-	public String print(Distance distance, Locale locale) {
-		return distance == null ? null : String.format("%s%s", distance.getValue(), distance.getUnit().toLowerCase(locale));
+	public String print(@Nullable Distance distance, Locale locale) {
+		return distance == null ? "null"
+				: String.format("%s%s", distance.getValue(), distance.getUnit().toLowerCase(locale));
 	}
 
 	@Override
@@ -78,7 +81,6 @@ public enum DistanceFormatter implements Converter<String, Distance>, Formatter<
 	 * in the {@link #SUPPORTED_METRICS} map.
 	 *
 	 * @param source must not be {@literal null}.
-	 * @return
 	 */
 	private static Distance doConvert(String source) {
 
@@ -101,7 +103,6 @@ public enum DistanceFormatter implements Converter<String, Distance>, Formatter<
 	 *
 	 * @param source the raw source {@link String}, must not be {@literal null} or empty.
 	 * @param metric the {@link Metric} detected keyed by the keyword it was detected for, must not be {@literal null}.
-	 * @return
 	 */
 	private static Distance fromString(String source, Entry<String, Metric> metric) {
 

src/main/java/org/springframework/data/geo/format/PointFormatter.java

@@ -23,6 +23,7 @@ import org.springframework.core.convert.converter.GenericConverter.ConvertiblePa
 import org.springframework.data.geo.Point;
 import org.springframework.format.Formatter;
 import org.springframework.lang.NonNull;
+import org.springframework.lang.Nullable;
 
 /**
  * Converter to parse two comma-separated doubles into a {@link Point}.
@@ -60,8 +61,8 @@ public enum PointFormatter implements Converter<String, Point>, Formatter<Point>
 	}
 
 	@Override
-	public String print(Point point, Locale locale) {
-		return point == null ? null : String.format("%s,%s", point.getY(), point.getX());
+	public String print(@Nullable Point point, Locale locale) {
+		return point == null ? "null" : String.format("%s,%s", point.getY(), point.getX());
 	}
 
 	@Override

src/main/java/org/springframework/data/history/RevisionSort.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.data.history;
 
+import java.io.Serial;
 import java.util.Arrays;
 
 import org.springframework.data.domain.Sort;
@@ -30,7 +31,7 @@ import org.springframework.util.Assert;
  */
 public class RevisionSort extends Sort {
 
-	private static final long serialVersionUID = 618238321589063537L;
+	private static final @Serial long serialVersionUID = 618238321589063537L;
 
 	private static final String PROPERTY = "__revisionNumber__";
 	private static final RevisionSort ASC = new RevisionSort(Direction.ASC);

src/main/java/org/springframework/data/mapping/Alias.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.data.mapping;
 
+import java.util.NoSuchElementException;
 import java.util.Objects;
 
 import org.springframework.lang.Nullable;
@@ -41,9 +42,9 @@ public final class Alias {
 	@SuppressWarnings("null") //
 	public static final Alias NONE = new Alias(null);
 
-	private final Object value;
+	private final @Nullable Object value;
 
-	private Alias(Object value) {
+	private Alias(@Nullable Object value) {
 		this.value = value;
 	}
 
@@ -104,7 +105,7 @@ public final class Alias {
 	}
 
 	/**
-	 * Returns whether the the current alias is present and has the same value as the given {@link Alias}.
+	 * Returns whether the current alias is present and has the same value as the given {@link Alias}.
 	 *
 	 * @param other the other {@link Alias}
 	 * @return {@literal true} if there's an alias value present and its equal to the one in the given {@link Alias}.
@@ -120,6 +121,14 @@ public final class Alias {
 		return value != null;
 	}
 
+	/**
+	 * @return {@literal true} if this {@link Alias} does not contain a value.
+	 * @since 4.0
+	 */
+	public boolean isEmpty() {
+		return value == null;
+	}
+
 	/**
 	 * Return the value typed to {@code type} if the value is present and assignable to {@code type}.
 	 *
@@ -135,15 +144,27 @@ public final class Alias {
 		return isPresent() && type.isInstance(value) ? (T) value : null;
 	}
 
-	@Override
-	public String toString() {
-		return isPresent() ? value.toString() : "NONE";
-	}
-
+	@Nullable
 	public Object getValue() {
 		return this.value;
 	}
 
+	/**
+	 * Retrieve the required value or throw {@link NoSuchElementException} if the value is {@link #isEmpty() absent}.
+	 *
+	 * @return the required value.
+	 */
+	public Object getRequiredValue() {
+
+		Object value = getValue();
+
+		if (value == null) {
+			throw new NoSuchElementException("No value present");
+		}
+
+		return value;
+	}
+
 	@Override
 	public boolean equals(@Nullable Object o) {
 
@@ -162,4 +183,9 @@ public final class Alias {
 	public int hashCode() {
 		return Objects.hashCode(value);
 	}
+
+	@Override
+	public String toString() {
+		return isPresent() ? value.toString() : "NONE";
+	}
 }

src/main/java/org/springframework/data/mapping/Association.java

@@ -32,8 +32,8 @@ public class Association<P extends PersistentProperty<P>> {
 	/**
 	 * Creates a new {@link Association} between the two given {@link PersistentProperty}s.
 	 *
-	 * @param inverse
-	 * @param obverse
+	 * @param inverse the inverse {@link PersistentProperty}.
+	 * @param obverse the obverse {@link PersistentProperty}. Can be {@literal null} if absent.
 	 */
 	public Association(P inverse, @Nullable P obverse) {
 		this.inverse = inverse;

src/main/java/org/springframework/data/mapping/MappingException.java

@@ -15,6 +15,8 @@
  */
 package org.springframework.data.mapping;
 
+import java.io.Serial;
+
 import org.springframework.lang.Nullable;
 
 /**
@@ -22,7 +24,7 @@ import org.springframework.lang.Nullable;
  */
 public class MappingException extends RuntimeException {
 
-	private static final long serialVersionUID = 1L;
+	private static final @Serial long serialVersionUID = 1L;
 
 	public MappingException(@Nullable String s) {
 		super(s);

src/main/java/org/springframework/data/mapping/Parameter.java

@@ -156,6 +156,7 @@ public class Parameter<T, P extends PersistentProperty<P>> {
 	 * @return the expression to be used when looking up a source data structure.
 	 * @since 3.3
 	 */
+	@SuppressWarnings("DataFlowIssue")
 	public String getRequiredValueExpression() {
 
 		if (!hasValueExpression()) {

src/main/java/org/springframework/data/mapping/PropertyReferenceException.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.data.mapping;
 
+import java.io.Serial;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.HashSet;
@@ -37,7 +38,7 @@ import org.springframework.util.StringUtils;
  */
 public class PropertyReferenceException extends RuntimeException {
 
-	private static final long serialVersionUID = -5254424051438976570L;
+	private static final @Serial long serialVersionUID = -5254424051438976570L;
 
 	static final String ERROR_TEMPLATE = "No property '%s' found for type '%s'";
 	static final String HINTS_TEMPLATE = "Did you mean %s";

src/main/java/org/springframework/data/mapping/callback/DefaultReactiveEntityCallbacks.java

@@ -99,6 +99,7 @@ class DefaultReactiveEntityCallbacks implements ReactiveEntityCallbacks {
 
 	static class DefaultReactiveEntityCallbackInvoker implements ReactiveEntityCallbackInvoker {
 
+		@SuppressWarnings("unchecked")
 		@Override
 		public <T> Mono<T> invokeCallback(EntityCallback<T> callback, T entity,
 				BiFunction<EntityCallback<T>, T, Object> callbackInvokerFunction) {

src/main/java/org/springframework/data/mapping/callback/EntityCallbackDiscoverer.java

@@ -53,11 +53,8 @@ class EntityCallbackDiscoverer {
 
 	private final CallbackRetriever defaultRetriever = new CallbackRetriever();
 	private final Map<CallbackCacheKey, CallbackRetriever> retrieverCache = new ConcurrentHashMap<>(64);
-	private final Map<Class<?>, ResolvableType> entityTypeCache = new ConcurrentHashMap<>(64);
 
-	@Nullable private ClassLoader beanClassLoader;
-
-	private Object retrievalMutex = this.defaultRetriever;
+	private @Nullable ClassLoader beanClassLoader;
 
 	/**
 	 * Create a new {@link EntityCallback} instance.
@@ -76,7 +73,7 @@ class EntityCallbackDiscoverer {
 
 		Assert.notNull(callback, "Callback must not be null");
 
-		synchronized (this.retrievalMutex) {
+		synchronized (this.defaultRetriever) {
 
 			// Explicitly remove target for a proxy, if registered already,
 			// in order to avoid double invocations of the same callback.
@@ -91,14 +88,6 @@ class EntityCallbackDiscoverer {
 		}
 	}
 
-	void removeEntityCallback(EntityCallback<?> callback) {
-
-		synchronized (this.retrievalMutex) {
-			this.defaultRetriever.entityCallbacks.remove(callback);
-			this.retrieverCache.clear();
-		}
-	}
-
 	/**
 	 * Return a {@link Collection} of all {@link EntityCallback}s matching the given entity type. Non-matching callbacks
 	 * get excluded early.
@@ -112,8 +101,7 @@ class EntityCallbackDiscoverer {
 	@SuppressWarnings({ "unchecked", "rawtypes" })
 	<T extends S, S> Collection<EntityCallback<S>> getEntityCallbacks(Class<T> entity, ResolvableType callbackType) {
 
-		Class<?> sourceType = entity;
-		CallbackCacheKey cacheKey = new CallbackCacheKey(callbackType, sourceType);
+		CallbackCacheKey cacheKey = new CallbackCacheKey(callbackType, entity);
 
 		// Quick check for existing entry on ConcurrentHashMap...
 		CallbackRetriever retriever = this.retrieverCache.get(cacheKey);
@@ -122,16 +110,16 @@ class EntityCallbackDiscoverer {
 		}
 
 		if (this.beanClassLoader == null || ClassUtils.isCacheSafe(entity, this.beanClassLoader)
-				&& (sourceType == null || ClassUtils.isCacheSafe(sourceType, this.beanClassLoader))) {
+				&& ClassUtils.isCacheSafe(entity, this.beanClassLoader)) {
 
 			// Fully synchronized building and caching of a CallbackRetriever
-			synchronized (this.retrievalMutex) {
+			synchronized (this.defaultRetriever) {
 				retriever = this.retrieverCache.get(cacheKey);
 				if (retriever != null) {
 					return (Collection) retriever.getEntityCallbacks();
 				}
 				retriever = new CallbackRetriever();
-				Collection<EntityCallback<?>> callbacks = retrieveEntityCallbacks(ResolvableType.forClass(sourceType),
+				Collection<EntityCallback<?>> callbacks = retrieveEntityCallbacks(ResolvableType.forClass(entity),
 						callbackType, retriever);
 				this.retrieverCache.put(cacheKey, retriever);
 				return (Collection) callbacks;
@@ -142,19 +130,6 @@ class EntityCallbackDiscoverer {
 		}
 	}
 
-	@Nullable
-	ResolvableType resolveDeclaredEntityType(Class<?> callbackType) {
-
-		ResolvableType eventType = entityTypeCache.get(callbackType);
-
-		if (eventType == null) {
-			eventType = ResolvableType.forClass(callbackType).as(EntityCallback.class).getGeneric();
-			entityTypeCache.put(callbackType, eventType);
-		}
-
-		return eventType != ResolvableType.NONE ? eventType : null;
-	}
-
 	/**
 	 * Actually retrieve the callbacks for the given entity and callback type.
 	 *
@@ -169,7 +144,7 @@ class EntityCallbackDiscoverer {
 		List<EntityCallback<?>> allCallbacks = new ArrayList<>();
 		Set<EntityCallback<?>> callbacks;
 
-		synchronized (this.retrievalMutex) {
+		synchronized (this.defaultRetriever) {
 			callbacks = new LinkedHashSet<>(this.defaultRetriever.entityCallbacks);
 		}
 
@@ -211,15 +186,12 @@ class EntityCallbackDiscoverer {
 			if (this.beanClassLoader == null) {
 				this.beanClassLoader = cbf.getBeanClassLoader();
 			}
-
-			this.retrievalMutex = cbf.getSingletonMutex();
 		}
 
 		defaultRetriever.discoverEntityCallbacks(beanFactory);
 		this.retrieverCache.clear();
 	}
 
-	@Nullable
 	static Method lookupCallbackMethod(Class<?> callbackType, Class<?> entityType, Object[] args) {
 
 		Collection<Method> methods = new ArrayList<>(1);
@@ -299,6 +271,7 @@ class EntityCallbackDiscoverer {
 			return this.entityCallbacks;
 		}
 
+		@SuppressWarnings("rawtypes")
 		void discoverEntityCallbacks(BeanFactory beanFactory) {
 
 			// We need both a ListableBeanFactory and BeanDefinitionRegistry here for advanced inspection.

src/main/java/org/springframework/data/mapping/callback/EntityCallbackInvoker.java

@@ -29,7 +29,6 @@ interface EntityCallbackInvoker {
 	 * @param callback must not be {@literal null}.
 	 * @param entity must not be {@literal null}
 	 * @param callbackInvokerFunction must not be {@literal null}.
-	 * @param <T>
 	 * @return never {@literal null}.
 	 */
 	<T> Object invokeCallback(EntityCallback<T> callback, T entity,

src/main/java/org/springframework/data/mapping/callback/ReactiveEntityCallbackInvoker.java

@@ -19,9 +19,6 @@ import reactor.core.publisher.Mono;
 
 import java.util.function.BiFunction;
 
-import org.springframework.lang.NonNull;
-import org.springframework.lang.Nullable;
-
 /**
  * @author Christoph Strobl
  * @since 2.2
@@ -32,11 +29,9 @@ interface ReactiveEntityCallbackInvoker extends EntityCallbackInvoker {
 	 * @param callback must not be {@literal null}.
 	 * @param entity can be {@literal null}
 	 * @param callbackInvokerFunction must not be {@literal null}.
-	 * @param <T>
 	 * @return a {@link Mono} emitting the result of the invocation.
 	 */
-	@NonNull
 	@Override
-	<T> Mono<T> invokeCallback(EntityCallback<T> callback, @Nullable T entity,
+	<T> Mono<T> invokeCallback(EntityCallback<T> callback, T entity,
 			BiFunction<EntityCallback<T>, T, Object> callbackInvokerFunction);
 }

src/main/java/org/springframework/data/mapping/callback/ReactiveEntityCallbacks.java

@@ -77,7 +77,7 @@ public interface ReactiveEntityCallbacks {
 	/**
 	 * Obtain a new {@link ReactiveEntityCallbacks} instance.
 	 * <p>
-	 * {@link EntityCallback callbacks} are pre loaded from the given {@link BeanFactory}. <br />
+	 * {@link EntityCallback callbacks} are pre-loaded from the given {@link BeanFactory}. <br />
 	 * Use {@link #addEntityCallback(EntityCallback)} to register additional callbacks manually.
 	 *
 	 * @param beanFactory must not be {@literal null}.

src/main/java/org/springframework/data/mapping/context/AbstractMappingContext.java

@@ -141,7 +141,7 @@ public abstract class AbstractMappingContext<E extends MutablePersistentEntity<?
 	 * already set.
 	 *
 	 * @param applicationContext the ApplicationContext object to be used by this object.
-	 * @throws BeansException
+	 * @throws BeansException in case of initialization errors.
 	 */
 	@Override
 	public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
@@ -159,7 +159,7 @@ public abstract class AbstractMappingContext<E extends MutablePersistentEntity<?
 
 	/**
 	 * @param beanFactory owning BeanFactory.
-	 * @throws BeansException
+	 * @throws BeansException in case of initialization errors.
 	 * @since 3.3
 	 */
 	@Override
@@ -565,9 +565,9 @@ public abstract class AbstractMappingContext<E extends MutablePersistentEntity<?
 
 	/**
 	 * Returns whether a {@link PersistentEntity} instance should be created for the given {@link TypeInformation}. By
-	 * default this will reject all types considered simple and non-supported Kotlin classes, but it might be necessary to
-	 * tweak that in case you have registered custom converters for top level types (which renders them to be considered
-	 * simple) but still need meta-information about them.
+	 * default, this will reject all types considered simple and non-supported Kotlin classes, but it might be necessary
+	 * to tweak that in case you have registered custom converters for top level types (which renders them to be
+	 * considered simple) but still need meta-information about them.
 	 *
 	 * @param type will never be {@literal null}.
 	 * @return
@@ -673,7 +673,7 @@ public abstract class AbstractMappingContext<E extends MutablePersistentEntity<?
 			});
 		}
 
-		protected boolean shouldSkipOverrideProperty(P property) {
+		private boolean shouldSkipOverrideProperty(P property) {
 
 			P existingProperty = entity.getPersistentProperty(property.getName());
 
@@ -758,7 +758,7 @@ public abstract class AbstractMappingContext<E extends MutablePersistentEntity<?
 	 *
 	 * @author Oliver Gierke
 	 */
-	static enum PersistentPropertyFilter implements FieldFilter {
+	enum PersistentPropertyFilter implements FieldFilter {
 
 		INSTANCE;
 

src/main/java/org/springframework/data/mapping/context/DefaultPersistentPropertyPath.java

@@ -24,6 +24,7 @@ import org.springframework.core.convert.converter.Converter;
 import org.springframework.data.mapping.PersistentProperty;
 import org.springframework.data.mapping.PersistentPropertyPath;
 import org.springframework.data.util.TypeInformation;
+import org.springframework.lang.Contract;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
@@ -56,7 +57,7 @@ class DefaultPersistentPropertyPath<P extends PersistentProperty<P>> implements
 	/**
 	 * Creates an empty {@link DefaultPersistentPropertyPath}.
 	 *
-	 * @return
+	 * @return an empty {@link DefaultPersistentPropertyPath}.
 	 */
 	static <T extends PersistentProperty<T>> DefaultPersistentPropertyPath<T> empty() {
 		return new DefaultPersistentPropertyPath<T>(Collections.emptyList());
@@ -206,6 +207,7 @@ class DefaultPersistentPropertyPath<P extends PersistentProperty<P>> implements
 	 * @param type can be {@literal null}.
 	 * @return
 	 */
+	@Contract("null -> false")
 	public boolean containsPropertyOfType(@Nullable TypeInformation<?> type) {
 
 		if (type == null) {

src/main/java/org/springframework/data/mapping/context/InvalidPersistentPropertyPath.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.data.mapping.context;
 
+import java.io.Serial;
 import java.util.Arrays;
 import java.util.HashSet;
 import java.util.Set;
@@ -36,7 +37,7 @@ import org.springframework.util.StringUtils;
  */
 public class InvalidPersistentPropertyPath extends MappingException {
 
-	private static final long serialVersionUID = 2805815643641094488L;
+	private static final @Serial long serialVersionUID = 2805815643641094488L;
 	private static final String DEFAULT_MESSAGE = "No property '%s' found on %s; Did you mean: %s";
 
 	private final String source;
@@ -109,9 +110,7 @@ public class InvalidPersistentPropertyPath extends MappingException {
 			return "";
 		}
 
-		String dotPath = path.toDotPath();
-
-		return dotPath == null ? "" : dotPath;
+		return path.toDotPath();
 	}
 
 	private static String createMessage(TypeInformation<?> type, String unresolvableSegment) {

src/main/java/org/springframework/data/mapping/context/MappingContextEvent.java

@@ -15,6 +15,8 @@
  */
 package org.springframework.data.mapping.context;
 
+import java.io.Serial;
+
 import org.springframework.context.ApplicationEvent;
 import org.springframework.data.mapping.PersistentEntity;
 import org.springframework.data.mapping.PersistentProperty;
@@ -31,7 +33,7 @@ import org.springframework.util.Assert;
 public class MappingContextEvent<E extends PersistentEntity<?, P>, P extends PersistentProperty<P>> extends
 		ApplicationEvent {
 
-	private static final long serialVersionUID = 1336466833846092490L;
+	private static final @Serial long serialVersionUID = 1336466833846092490L;
 
 	private final MappingContext<?, ?> source;
 	private final E entity;

src/main/java/org/springframework/data/mapping/context/PersistentEntities.java

@@ -53,7 +53,6 @@ public class PersistentEntities implements Streamable<PersistentEntity<?, ? exte
 	 *
 	 * @param contexts
 	 */
-	@SuppressWarnings("unchecked")
 	public PersistentEntities(Iterable<? extends MappingContext<?, ?>> contexts) {
 
 		Assert.notNull(contexts, "MappingContexts must not be null");
@@ -208,7 +207,7 @@ public class PersistentEntities implements Streamable<PersistentEntity<?, ? exte
 
 	/**
 	 * Returns the type the given {@link PersistentProperty} ultimately refers to. In case it's of a unique identifier
-	 * type of an entity known it'll return the entity type.
+	 * type of entity known it'll return the entity type.
 	 *
 	 * @param property must not be {@literal null}.
 	 * @return

src/main/java/org/springframework/data/mapping/context/PersistentPropertyPathFactory.java

@@ -436,8 +436,8 @@ class PersistentPropertyPathFactory<E extends PersistentEntity<?, P>, P extends
 
 		private final PersistentPropertyPath<?> path;
 		private final boolean resolvable;
-		private @Nullable final String source;
 
+		private @Nullable final String source;
 		private @Nullable final String segment;
 		private @Nullable final TypeInformation<?> type;
 

src/main/java/org/springframework/data/mapping/model/BasicPersistentEntity.java

@@ -132,7 +132,6 @@ public class BasicPersistentEntity<T, P extends PersistentProperty<P>> implement
 
 	@Nullable
 	@Override
-	@SuppressWarnings("unchecked")
 	public PreferredConstructor<T, P> getPersistenceConstructor() {
 		return creator instanceof PreferredConstructor ? (PreferredConstructor<T, P>) creator : null;
 	}
@@ -556,15 +555,8 @@ public class BasicPersistentEntity<T, P extends PersistentProperty<P>> implement
 	 *
 	 * @author Oliver Gierke
 	 */
-	private static final class AssociationComparator<P extends PersistentProperty<P>>
-			implements Comparator<Association<P>>, Serializable {
-
-		private static final long serialVersionUID = 4508054194886854513L;
-		private final Comparator<P> delegate;
-
-		AssociationComparator(Comparator<P> delegate) {
-			this.delegate = delegate;
-		}
+	private record AssociationComparator<P extends PersistentProperty<P>>(
+			Comparator<P> delegate) implements Comparator<Association<P>>, Serializable {
 
 		@Override
 		public int compare(@Nullable Association<P> left, @Nullable Association<P> right) {

src/main/java/org/springframework/data/mapping/model/BeanWrapper.java

@@ -141,7 +141,7 @@ class BeanWrapper<T> implements PersistentPropertyAccessor<T> {
 
 		} catch (IllegalStateException e) {
 			throw new MappingException(
-					String.format("Could not read property %s of %s", property.toString(), bean.toString()), e);
+					String.format("Could not read property %s of %s", property, bean.toString()), e);
 		}
 	}
 

src/main/java/org/springframework/data/mapping/model/BytecodeUtil.java

@@ -209,7 +209,7 @@ abstract class BytecodeUtil {
 	 * Returns the signature type for a {@link Class} including primitives.
 	 *
 	 * @param type must not be {@literal null}
-	 * @return
+	 * @return bytecode type name in the form of {@literal Ljava/lang/Object;}.
 	 */
 	static String signatureTypeName(Class<?> type) {
 

src/main/java/org/springframework/data/mapping/model/ClassGeneratingPropertyAccessorFactory.java

@@ -379,12 +379,10 @@ public class ClassGeneratingPropertyAccessorFactory implements PersistentPropert
 			final List<PersistentProperty<?>> persistentProperties = new ArrayList<>();
 
 			entity.doWithAssociations((SimpleAssociationHandler) association -> {
-				if (association.getInverse() != null) {
-					persistentProperties.add(association.getInverse());
-				}
+				persistentProperties.add(association.getInverse());
 			});
 
-			entity.doWithProperties((SimplePropertyHandler) property -> persistentProperties.add(property));
+			entity.doWithProperties((SimplePropertyHandler) persistentProperties::add);
 
 			return persistentProperties;
 		}
@@ -583,9 +581,9 @@ public class ClassGeneratingPropertyAccessorFactory implements PersistentPropert
 						// keep it a lambda to infer the correct types, preventing
 						// LambdaConversionException: Invalid receiver type class java.lang.reflect.AccessibleObject; not a subtype
 						// of implementation type interface java.lang.reflect.Member
-						.map(it -> it.getDeclaringClass());
+						.map(Member::getDeclaringClass);
 
-			}).collect(Collectors.collectingAndThen(Collectors.toSet(), it -> new ArrayList<>(it)));
+			}).collect(Collectors.collectingAndThen(Collectors.toSet(), ArrayList::new));
 
 		}
 

src/main/java/org/springframework/data/mapping/model/ConvertingPropertyAccessor.java

@@ -19,6 +19,7 @@ import org.springframework.core.convert.ConversionService;
 import org.springframework.data.mapping.PersistentProperty;
 import org.springframework.data.mapping.PersistentPropertyAccessor;
 import org.springframework.data.mapping.PersistentPropertyPath;
+import org.springframework.lang.Contract;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
@@ -99,6 +100,7 @@ public class ConvertingPropertyAccessor<T> extends SimplePersistentPropertyPathA
 	 * @return
 	 */
 	@Nullable
+	@Contract("null, _ -> null")
 	@SuppressWarnings("unchecked")
 	private <S> S convertIfNecessary(@Nullable Object source, Class<S> type) {
 

src/main/java/org/springframework/data/mapping/model/KotlinInstantiationDelegate.java

@@ -101,14 +101,8 @@ class KotlinInstantiationDelegate {
 
 	/**
 	 * Extract the actual construction arguments for a direct constructor call.
-	 *
-	 * @param params
-	 * @param entityCreator
-	 * @param provider
-	 * @return
-	 * @param <P>
 	 */
-	public <P extends PersistentProperty<P>> Object[] extractInvocationArguments(Object[] params,
+	public <P extends PersistentProperty<P>> void extractInvocationArguments(Object[] params,
 			@Nullable InstanceCreatorMetadata<P> entityCreator, ParameterValueProvider<P> provider) {
 
 		if (entityCreator == null) {
@@ -155,8 +149,6 @@ class KotlinInstantiationDelegate {
 		for (int i = 0; i < defaulting.length; i++) {
 			params[userParameterCount + i] = defaulting[i];
 		}
-
-		return params;
 	}
 
 	/**
@@ -214,7 +206,7 @@ class KotlinInstantiationDelegate {
 				}
 			} else {
 
-				int optionalParameterCount = (int) kotlinFunction.getParameters().stream().filter(it -> it.isOptional())
+				int optionalParameterCount = (int) kotlinFunction.getParameters().stream().filter(KParameter::isOptional)
 						.count();
 				int syntheticParameters = KotlinDefaultMask.getExactMaskCount(optionalParameterCount);
 

src/main/java/org/springframework/data/mapping/model/MappingInstantiationException.java

@@ -18,6 +18,7 @@ package org.springframework.data.mapping.model;
 import kotlin.reflect.KFunction;
 import kotlin.reflect.jvm.ReflectJvmMapping;
 
+import java.io.Serial;
 import java.lang.reflect.Constructor;
 import java.lang.reflect.Method;
 import java.util.ArrayList;
@@ -43,7 +44,7 @@ import org.springframework.util.ObjectUtils;
  */
 public class MappingInstantiationException extends RuntimeException {
 
-	private static final long serialVersionUID = 822211065035487628L;
+	private static final @Serial long serialVersionUID = 822211065035487628L;
 	private static final String TEXT_TEMPLATE = "Failed to instantiate %s using constructor %s with arguments %s";
 
 	private final Class<?> entityType;

src/main/java/org/springframework/data/mapping/model/ParameterValueProvider.java

@@ -30,7 +30,7 @@ public interface ParameterValueProvider<P extends PersistentProperty<P>> {
 	 * Returns the value to be used for the given {@link Parameter} (usually when entity instances are created).
 	 *
 	 * @param parameter must not be {@literal null}.
-	 * @return
+	 * @return the property value. Can be {@literal null}.
 	 */
 	@Nullable
 	<T> T getParameterValue(Parameter<T, P> parameter);

src/main/java/org/springframework/data/mapping/model/PersistentEntityParameterValueProvider.java

@@ -24,9 +24,7 @@ import org.springframework.lang.Nullable;
 
 /**
  * {@link ParameterValueProvider} based on a {@link PersistentEntity} to use a {@link PropertyValueProvider} to lookup
- * the value of the property referenced by the given {@link Parameter}. Additionally a
- * {@link DefaultSpELExpressionEvaluator} can be configured to get property value resolution trumped by a SpEL
- * expression evaluation.
+ * the value of the property referenced by the given {@link Parameter}.
  *
  * @author Oliver Gierke
  * @author Johannes Englmeier
@@ -39,7 +37,7 @@ public class PersistentEntityParameterValueProvider<P extends PersistentProperty
 	private final @Nullable Object parent;
 
 	public PersistentEntityParameterValueProvider(PersistentEntity<?, P> entity, PropertyValueProvider<P> provider,
-			Object parent) {
+			@Nullable Object parent) {
 		this.entity = entity;
 		this.provider = provider;
 		this.parent = parent;