Consistently declare Object::equals argument as @Nullable

spring-aop/src/main/java/org/springframework/aop/aspectj/TypePatternClassFilter.java

@@ -117,7 +117,7 @@ public class TypePatternClassFilter implements ClassFilter {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		return (this == obj || (obj instanceof TypePatternClassFilter that &&
 				ObjectUtils.nullSafeEquals(this.typePattern, that.typePattern)));
 	}

spring-aop/src/main/java/org/springframework/aop/support/RootClassFilter.java

@@ -19,6 +19,7 @@ package org.springframework.aop.support;
 import java.io.Serializable;
 
 import org.springframework.aop.ClassFilter;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -45,7 +46,7 @@ public class RootClassFilter implements ClassFilter, Serializable {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		return (this == obj || (obj instanceof RootClassFilter that &&
 				this.clazz.equals(that.clazz)));
 	}

spring-aop/src/main/java/org/springframework/aop/support/annotation/AnnotationMatchingPointcut.java

@@ -183,7 +183,7 @@ public class AnnotationMatchingPointcut implements Pointcut {
 		}
 
 		@Override
-		public boolean equals(Object obj) {
+		public boolean equals(@Nullable Object obj) {
 			if (this == obj) {
 				return true;
 			}

spring-aop/src/testFixtures/java/org/springframework/aop/testfixture/advice/MethodCounter.java

@@ -21,6 +21,8 @@ import java.lang.reflect.Method;
 import java.util.HashMap;
 import java.util.Map;
 
+import org.springframework.lang.Nullable;
+
 /**
  * Abstract superclass for counting advices etc.
  *
@@ -59,7 +61,7 @@ public class MethodCounter implements Serializable {
 	 * @see java.lang.Object#equals(java.lang.Object)
 	 */
 	@Override
-	public boolean equals(Object other) {
+	public boolean equals(@Nullable Object other) {
 		return (other != null && other.getClass() == this.getClass());
 	}
 

spring-aop/src/testFixtures/java/org/springframework/aop/testfixture/interceptor/NopInterceptor.java

@@ -19,6 +19,8 @@ package org.springframework.aop.testfixture.interceptor;
 import org.aopalliance.intercept.MethodInterceptor;
 import org.aopalliance.intercept.MethodInvocation;
 
+import org.springframework.lang.Nullable;
+
 /**
  * Trivial interceptor that can be introduced in a chain to display it.
  *
@@ -45,14 +47,14 @@ public class NopInterceptor implements MethodInterceptor {
 
 
 	@Override
-	public boolean equals(Object other) {
-		if (!(other instanceof NopInterceptor)) {
-			return false;
-		}
-		if (this == other) {
+	public boolean equals(@Nullable Object obj) {
+		if (this == obj) {
 			return true;
 		}
-		return this.count == ((NopInterceptor) other).count;
+		if (!(obj instanceof NopInterceptor that)) {
+			return false;
+		}
+		return this.count == that.count;
 	}
 
 	@Override

spring-aspects/src/test/java/org/springframework/cache/config/TestEntity.java

@@ -16,6 +16,7 @@
 
 package org.springframework.cache.config;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.ObjectUtils;
 
 /**
@@ -45,16 +46,11 @@ public class TestEntity {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (obj == this) {
 			return true;
 		}
-		if (obj == null) {
-			return false;
-		}
-		if (obj instanceof TestEntity) {
-			return ObjectUtils.nullSafeEquals(this.id, ((TestEntity) obj).id);
-		}
-		return false;
+		return (obj instanceof TestEntity that && ObjectUtils.nullSafeEquals(this.id, that.id));
 	}
+
 }

spring-beans/src/test/java/org/springframework/beans/factory/DefaultListableBeanFactoryTests.java

@@ -2821,7 +2821,7 @@ class DefaultListableBeanFactoryTests {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o) {
 				return true;
 			}

spring-beans/src/test/java/org/springframework/beans/support/PagedListHolderTests.java

@@ -22,6 +22,7 @@ import java.util.List;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.beans.testfixture.beans.TestBean;
+import org.springframework.lang.Nullable;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -194,7 +195,7 @@ public class PagedListHolderTests {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o) {
 				return true;
 			}

spring-beans/src/testFixtures/java/org/springframework/beans/testfixture/beans/NestedTestBean.java

@@ -16,6 +16,8 @@
 
 package org.springframework.beans.testfixture.beans;
 
+import org.springframework.lang.Nullable;
+
 /**
  * Simple nested test bean used for testing bean factories, AOP framework etc.
  *
@@ -43,7 +45,7 @@ public class NestedTestBean implements INestedTestBean {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (!(obj instanceof NestedTestBean ntb)) {
 			return false;
 		}

spring-beans/src/testFixtures/java/org/springframework/beans/testfixture/beans/Pet.java

@@ -16,6 +16,8 @@
 
 package org.springframework.beans.testfixture.beans;
 
+import org.springframework.lang.Nullable;
+
 /**
  * @author Rob Harrop
  * @since 2.0
@@ -38,7 +40,7 @@ public class Pet {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 		if (this == o) {
 			return true;
 		}

spring-beans/src/testFixtures/java/org/springframework/beans/testfixture/beans/SerializablePerson.java

@@ -18,6 +18,7 @@ package org.springframework.beans.testfixture.beans;
 
 import java.io.Serializable;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.ObjectUtils;
 
 /**
@@ -63,7 +64,7 @@ public class SerializablePerson implements Person, Serializable {
 
 
 	@Override
-	public boolean equals(Object other) {
+	public boolean equals(@Nullable Object other) {
 		if (!(other instanceof SerializablePerson p)) {
 			return false;
 		}

spring-beans/src/testFixtures/java/org/springframework/beans/testfixture/beans/TestBean.java

@@ -30,6 +30,7 @@ import java.util.Set;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryAware;
 import org.springframework.beans.factory.BeanNameAware;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ObjectUtils;
 
 /**
@@ -464,7 +465,7 @@ public class TestBean implements BeanNameAware, BeanFactoryAware, ITestBean, IOt
 
 
 	@Override
-	public boolean equals(Object other) {
+	public boolean equals(@Nullable Object other) {
 		if (this == other) {
 			return true;
 		}

spring-context/src/main/java/org/springframework/scheduling/support/BitsCronField.java

@@ -256,7 +256,7 @@ final class BitsCronField extends CronField {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 		if (this == o) {
 			return true;
 		}

spring-context/src/main/java/org/springframework/scheduling/support/CompositeCronField.java

@@ -77,7 +77,7 @@ final class CompositeCronField extends CronField {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 		if (this == o) {
 			return true;
 		}

spring-context/src/main/java/org/springframework/scheduling/support/CronExpression.java

@@ -273,7 +273,7 @@ public final class CronExpression {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 		if (this == o) {
 			return true;
 		}

spring-context/src/main/java/org/springframework/scheduling/support/QuartzCronField.java

@@ -359,7 +359,7 @@ final class QuartzCronField extends CronField {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 		if (this == o) {
 			return true;
 		}

spring-context/src/test/java/org/springframework/aop/framework/AbstractAopProxyTests.java

@@ -1651,7 +1651,7 @@ public abstract class AbstractAopProxyTests {
 	public static class AllInstancesAreEqual implements IOther {
 
 		@Override
-		public boolean equals(Object other) {
+		public boolean equals(@Nullable Object other) {
 			return (other instanceof AllInstancesAreEqual);
 		}
 

spring-context/src/test/java/org/springframework/aop/framework/CglibProxyTests.java

@@ -35,6 +35,7 @@ import org.springframework.beans.testfixture.beans.TestBean;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextException;
 import org.springframework.context.support.ClassPathXmlApplicationContext;
+import org.springframework.lang.Nullable;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
@@ -214,7 +215,7 @@ public class CglibProxyTests extends AbstractAopProxyTests implements Serializab
 				return MethodMatcher.TRUE;
 			}
 			@Override
-			public boolean equals(Object obj) {
+			public boolean equals(@Nullable Object obj) {
 				return true;
 			}
 			@Override

spring-context/src/test/java/org/springframework/aop/framework/JdkDynamicProxyTests.java

@@ -27,6 +27,7 @@ import org.springframework.aop.support.AopUtils;
 import org.springframework.beans.testfixture.beans.IOther;
 import org.springframework.beans.testfixture.beans.ITestBean;
 import org.springframework.beans.testfixture.beans.TestBean;
+import org.springframework.lang.Nullable;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
@@ -197,7 +198,7 @@ public class JdkDynamicProxyTests extends AbstractAopProxyTests implements Seria
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o) {
 				return true;
 			}

spring-context/src/test/java/org/springframework/context/annotation/AnnotationConfigApplicationContextTests.java

@@ -37,6 +37,7 @@ import org.springframework.context.annotation6.Jsr330NamedForScanning;
 import org.springframework.context.testfixture.context.annotation.CglibConfiguration;
 import org.springframework.context.testfixture.context.annotation.LambdaBeanConfiguration;
 import org.springframework.core.ResolvableType;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ObjectUtils;
 
 import static java.lang.String.format;
@@ -732,7 +733,7 @@ class TestBean {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (this == obj) {
 			return true;
 		}

spring-context/src/test/java/org/springframework/context/event/test/AbstractIdentifiable.java

@@ -18,6 +18,8 @@ package org.springframework.context.event.test;
 
 import java.util.UUID;
 
+import org.springframework.lang.Nullable;
+
 /**
  * @author Stephane Nicoll
  */
@@ -35,7 +37,7 @@ public abstract class AbstractIdentifiable implements Identifiable {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 		if (this == o) {
 			return true;
 		}

spring-context/src/test/java/org/springframework/context/event/test/GenericEventPojo.java

@@ -18,6 +18,7 @@ package org.springframework.context.event.test;
 
 import org.springframework.core.ResolvableType;
 import org.springframework.core.ResolvableTypeProvider;
+import org.springframework.lang.Nullable;
 
 /**
  * A simple POJO that implements {@link ResolvableTypeProvider}.
@@ -37,7 +38,7 @@ public class GenericEventPojo<T> implements ResolvableTypeProvider {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 		if (this == o) {
 			return true;
 		}

spring-context/src/test/java/org/springframework/context/event/test/IdentifiableApplicationEvent.java

@@ -19,6 +19,7 @@ package org.springframework.context.event.test;
 import java.util.UUID;
 
 import org.springframework.context.ApplicationEvent;
+import org.springframework.lang.Nullable;
 
 /**
  * A basic test event that can be uniquely identified easily.
@@ -49,7 +50,7 @@ public abstract class IdentifiableApplicationEvent extends ApplicationEvent impl
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 		if (this == o) {
 			return true;
 		}

spring-context/src/test/java/org/springframework/jmx/export/TestDynamicMBean.java

@@ -25,6 +25,8 @@ import javax.management.MBeanInfo;
 import javax.management.MBeanNotificationInfo;
 import javax.management.MBeanOperationInfo;
 
+import org.springframework.lang.Nullable;
+
 /**
  * @author Rob Harrop
  * @author Juergen Hoeller
@@ -76,7 +78,7 @@ public class TestDynamicMBean implements DynamicMBean {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		return (obj instanceof TestDynamicMBean);
 	}
 

spring-context/src/test/java/org/springframework/ui/ModelMapTests.java

@@ -29,6 +29,7 @@ import org.junit.jupiter.api.Test;
 
 import org.springframework.aop.framework.ProxyFactory;
 import org.springframework.beans.testfixture.beans.TestBean;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.StringUtils;
 
@@ -288,7 +289,7 @@ public class ModelMapTests {
 	public static class SomeInnerClass {
 
 		@Override
-		public boolean equals(Object obj) {
+		public boolean equals(@Nullable Object obj) {
 			return (obj instanceof SomeInnerClass);
 		}
 

spring-context/src/testFixtures/java/org/springframework/context/testfixture/cache/beans/TestEntity.java

@@ -16,6 +16,7 @@
 
 package org.springframework.context.testfixture.cache.beans;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.ObjectUtils;
 
 /**
@@ -41,16 +42,11 @@ public class TestEntity {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (obj == this) {
 			return true;
 		}
-		if (obj == null) {
-			return false;
-		}
-		if (obj instanceof TestEntity) {
-			return ObjectUtils.nullSafeEquals(this.id, ((TestEntity) obj).id);
-		}
-		return false;
+		return (obj instanceof TestEntity that && ObjectUtils.nullSafeEquals(this.id, that.id));
 	}
+
 }

spring-core-test/src/main/java/org/springframework/aot/agent/MethodReference.java

@@ -18,6 +18,8 @@ package org.springframework.aot.agent;
 
 import java.util.Objects;
 
+import org.springframework.lang.Nullable;
+
 /**
  * Reference to a Java method, identified by its owner class and the method name.
  *
@@ -61,7 +63,7 @@ public final class MethodReference {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 		if (this == o) {
 			return true;
 		}

spring-core-test/src/main/java/org/springframework/core/test/tools/ClassFiles.java

@@ -117,7 +117,7 @@ public final class ClassFiles implements Iterable<ClassFile> {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (this == obj) {
 			return true;
 		}

spring-core-test/src/main/java/org/springframework/core/test/tools/DynamicFile.java

@@ -20,6 +20,7 @@ import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -81,7 +82,7 @@ public abstract sealed class DynamicFile permits SourceFile, ResourceFile {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (this == obj) {
 			return true;
 		}

spring-core-test/src/main/java/org/springframework/core/test/tools/DynamicFiles.java

@@ -102,7 +102,7 @@ final class DynamicFiles<F extends DynamicFile> implements Iterable<F> {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (this == obj) {
 			return true;
 		}

spring-core-test/src/main/java/org/springframework/core/test/tools/ResourceFiles.java

@@ -131,7 +131,7 @@ public final class ResourceFiles implements Iterable<ResourceFile> {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (this == obj) {
 			return true;
 		}

spring-core-test/src/main/java/org/springframework/core/test/tools/SourceFiles.java

@@ -160,7 +160,7 @@ public final class SourceFiles implements Iterable<SourceFile> {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (this == obj) {
 			return true;
 		}

spring-core/src/main/java/org/springframework/aot/generate/MethodName.java

@@ -96,7 +96,7 @@ final class MethodName {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (this == obj) {
 			return true;
 		}

spring-core/src/main/java/org/springframework/aot/hint/AbstractTypeReference.java

@@ -83,7 +83,7 @@ public abstract class AbstractTypeReference implements TypeReference {
 	}
 
 	@Override
-	public boolean equals(Object other) {
+	public boolean equals(@Nullable Object other) {
 		if (this == other) {
 			return true;
 		}

spring-core/src/main/java/org/springframework/aot/hint/JavaSerializationHint.java

@@ -56,7 +56,7 @@ public class JavaSerializationHint implements ConditionalHint {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 		if (this == o) {
 			return true;
 		}

spring-core/src/main/java/org/springframework/aot/hint/JdkProxyHint.java

@@ -77,7 +77,7 @@ public final class JdkProxyHint implements ConditionalHint {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 		if (this == o) {
 			return true;
 		}

spring-core/src/main/java/org/springframework/aot/hint/ResourceBundleHint.java

@@ -56,7 +56,7 @@ public final class ResourceBundleHint implements ConditionalHint {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 		if (this == o) {
 			return true;
 		}

spring-core/src/main/java/org/springframework/aot/hint/ResourcePatternHint.java

@@ -98,7 +98,7 @@ public final class ResourcePatternHint implements ConditionalHint {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 		if (this == o) {
 			return true;
 		}

spring-core/src/main/java/org/springframework/aot/hint/TypeHint.java

@@ -287,7 +287,7 @@ public final class TypeHint implements ConditionalHint {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o) {
 				return true;
 			}

spring-core/src/main/java/org/springframework/core/env/ProfilesParser.java

@@ -174,7 +174,7 @@ final class ProfilesParser {
 		}
 
 		@Override
-		public boolean equals(Object obj) {
+		public boolean equals(@Nullable Object obj) {
 			if (this == obj) {
 				return true;
 			}

spring-core/src/main/java/org/springframework/util/UnmodifiableMultiValueMap.java

@@ -125,7 +125,7 @@ final class UnmodifiableMultiValueMap<K,V> implements MultiValueMap<K,V>, Serial
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		return this == obj || this.delegate.equals(obj);
 	}
 
@@ -362,7 +362,7 @@ final class UnmodifiableMultiValueMap<K,V> implements MultiValueMap<K,V>, Serial
 		}
 
 		@Override
-		public boolean equals(Object obj) {
+		public boolean equals(@Nullable Object obj) {
 			if (this == obj) {
 				return true;
 			}
@@ -508,7 +508,7 @@ final class UnmodifiableMultiValueMap<K,V> implements MultiValueMap<K,V>, Serial
 			}
 
 			@Override
-			public boolean equals(Object obj) {
+			public boolean equals(@Nullable Object obj) {
 				if (this == obj) {
 					return true;
 				}
@@ -625,7 +625,7 @@ final class UnmodifiableMultiValueMap<K,V> implements MultiValueMap<K,V>, Serial
 		}
 
 		@Override
-		public boolean equals(Object obj) {
+		public boolean equals(@Nullable Object obj) {
 			return this == obj || this.delegate.equals(obj);
 		}
 

spring-core/src/test/java/org/springframework/core/convert/converter/DefaultConversionServiceTests.java

@@ -49,6 +49,7 @@ import org.springframework.core.convert.ConversionFailedException;
 import org.springframework.core.convert.ConverterNotFoundException;
 import org.springframework.core.convert.TypeDescriptor;
 import org.springframework.core.convert.support.DefaultConversionService;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -1045,7 +1046,7 @@ class DefaultConversionServiceTests {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (!(o instanceof SSN ssn)) {
 				return false;
 			}
@@ -1085,7 +1086,7 @@ class DefaultConversionServiceTests {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (!(o instanceof ISBN isbn)) {
 				return false;
 			}

spring-core/src/test/java/org/springframework/core/type/CachingMetadataReaderLeakTests.java

@@ -26,6 +26,7 @@ import org.springframework.core.testfixture.EnabledForTestGroups;
 import org.springframework.core.type.classreading.CachingMetadataReaderFactory;
 import org.springframework.core.type.classreading.MetadataReader;
 import org.springframework.core.type.classreading.MetadataReaderFactory;
+import org.springframework.lang.Nullable;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.springframework.core.testfixture.TestGroup.LONG_RUNNING;
@@ -56,7 +57,7 @@ class CachingMetadataReaderLeakTests {
 			Resource resource = new UrlResource(url) {
 
 				@Override
-				public boolean equals(Object obj) {
+				public boolean equals(@Nullable Object obj) {
 					return (obj == this);
 				}
 

spring-core/src/test/java/org/springframework/util/CollectionUtilsTests.java

@@ -29,6 +29,8 @@ import java.util.Set;
 
 import org.junit.jupiter.api.Test;
 
+import org.springframework.lang.Nullable;
+
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**
@@ -219,7 +221,7 @@ class CollectionUtilsTests {
 		}
 
 		@Override
-		public boolean equals(Object rhs) {
+		public boolean equals(@Nullable Object rhs) {
 			if (this == rhs) {
 				return true;
 			}

spring-core/src/test/java/org/springframework/util/xml/AbstractStaxXMLReaderTests.java

@@ -43,6 +43,7 @@ import org.xml.sax.helpers.AttributesImpl;
 
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.Resource;
+import org.springframework.lang.Nullable;
 import org.springframework.tests.MockitoUtils;
 import org.springframework.tests.MockitoUtils.InvocationArgumentsAdapter;
 
@@ -261,7 +262,7 @@ abstract class AbstractStaxXMLReaderTests {
 		}
 
 		@Override
-		public boolean equals(Object obj) {
+		public boolean equals(@Nullable Object obj) {
 			Attributes other = ((PartialAttributes) obj).attributes;
 			if (this.attributes.getLength() != other.getLength()) {
 				return false;

spring-core/src/testFixtures/java/org/springframework/core/testfixture/security/TestPrincipal.java

@@ -18,6 +18,8 @@ package org.springframework.core.testfixture.security;
 
 import java.security.Principal;
 
+import org.springframework.lang.Nullable;
+
 /**
  * An implementation of {@link Principal} for testing.
  *
@@ -37,7 +39,7 @@ public class TestPrincipal implements Principal {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (obj == this) {
 			return true;
 		}

spring-expression/src/test/java/org/springframework/expression/spel/SpelReproTests.java

@@ -2251,7 +2251,7 @@ class SpelReproTests extends AbstractExpressionTests {
 		}
 
 		@Override
-		public boolean equals(Object other) {
+		public boolean equals(@Nullable Object other) {
 			return (this == other || (other instanceof TestClass2 &&
 					this.string.equals(((TestClass2) other).string)));
 		}

spring-expression/src/test/java/org/springframework/expression/spel/testresources/PlaceOfBirth.java

@@ -16,6 +16,8 @@
 
 package org.springframework.expression.spel.testresources;
 
+import org.springframework.lang.Nullable;
+
 ///CLOVER:OFF
 public class PlaceOfBirth {
 
@@ -51,7 +53,7 @@ public class PlaceOfBirth {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 		if (!(o instanceof PlaceOfBirth otherPOB)) {
 			return false;
 		}

spring-jms/src/test/java/org/springframework/jms/support/converter/MappingJackson2MessageConverterTests.java

@@ -33,6 +33,7 @@ import org.junit.jupiter.api.Test;
 import org.mockito.stubbing.Answer;
 
 import org.springframework.core.MethodParameter;
+import org.springframework.lang.Nullable;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
@@ -276,7 +277,7 @@ class MappingJackson2MessageConverterTests {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o) {
 				return true;
 			}

spring-messaging/src/test/java/org/springframework/messaging/simp/user/TestSimpSession.java

@@ -19,6 +19,8 @@ package org.springframework.messaging.simp.user;
 import java.util.HashSet;
 import java.util.Set;
 
+import org.springframework.lang.Nullable;
+
 /**
  * @author Rossen Stoyanchev
  */
@@ -64,8 +66,8 @@ public class TestSimpSession implements SimpSession {
 
 
 	@Override
-	public boolean equals(Object other) {
-		return (this == other || (other instanceof SimpSession && this.id.equals(((SimpSession) other).getId())));
+	public boolean equals(@Nullable Object obj) {
+		return (this == obj || (obj instanceof SimpSession that && this.id.equals(that.getId())));
 	}
 
 	@Override

spring-messaging/src/test/java/org/springframework/messaging/simp/user/TestSimpSubscription.java

@@ -16,6 +16,7 @@
 
 package org.springframework.messaging.simp.user;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.ObjectUtils;
 
 /**
@@ -57,7 +58,7 @@ public class TestSimpSubscription implements SimpSubscription {
 
 
 	@Override
-	public boolean equals(Object other) {
+	public boolean equals(@Nullable Object other) {
 		if (this == other) {
 			return true;
 		}

spring-messaging/src/test/java/org/springframework/messaging/simp/user/TestSimpUser.java

@@ -74,7 +74,7 @@ public class TestSimpUser implements SimpUser {
 
 
 	@Override
-	public boolean equals(Object other) {
+	public boolean equals(@Nullable Object other) {
 		return (this == other || (other instanceof SimpUser && this.name.equals(((SimpUser) other).getName())));
 	}
 

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/NamedParameterUtils.java

@@ -398,7 +398,7 @@ abstract class NamedParameterUtils {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o) {
 				return true;
 			}

spring-r2dbc/src/main/java/org/springframework/r2dbc/core/Parameter.java

@@ -111,7 +111,7 @@ public final class Parameter {
 
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (this == obj) {
 			return true;
 		}

spring-test/src/main/java/org/springframework/test/context/support/DynamicPropertiesContextCustomizer.java

@@ -26,6 +26,7 @@ import java.util.function.Supplier;
 
 import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.core.env.MutablePropertySources;
+import org.springframework.lang.Nullable;
 import org.springframework.test.context.ContextCustomizer;
 import org.springframework.test.context.DynamicPropertyRegistry;
 import org.springframework.test.context.DynamicPropertySource;
@@ -96,7 +97,7 @@ class DynamicPropertiesContextCustomizer implements ContextCustomizer {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (this == obj) {
 			return true;
 		}

spring-test/src/main/java/org/springframework/test/web/reactive/server/XpathAssertions.java

@@ -190,7 +190,7 @@ public class XpathAssertions {
 
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		throw new AssertionError("Object#equals is disabled " +
 				"to avoid being used in error instead of XPathAssertions#isEqualTo(String).");
 	}

spring-test/src/test/java/org/springframework/test/web/Person.java

@@ -19,6 +19,7 @@ package org.springframework.test.web;
 import jakarta.validation.constraints.NotNull;
 import jakarta.xml.bind.annotation.XmlRootElement;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.ObjectUtils;
 
 @XmlRootElement
@@ -66,7 +67,7 @@ public class Person {
 	}
 
 	@Override
-	public boolean equals(Object other) {
+	public boolean equals(@Nullable Object other) {
 		if (this == other) {
 			return true;
 		}

spring-test/src/test/java/org/springframework/test/web/reactive/server/samples/Person.java

@@ -20,6 +20,8 @@ import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import jakarta.xml.bind.annotation.XmlRootElement;
 
+import org.springframework.lang.Nullable;
+
 @XmlRootElement
 class Person {
 
@@ -44,7 +46,7 @@ class Person {
 	}
 
 	@Override
-	public boolean equals(Object other) {
+	public boolean equals(@Nullable Object other) {
 		if (this == other) {
 			return true;
 		}

spring-web/src/main/java/org/springframework/http/DefaultHttpStatusCode.java

@@ -19,6 +19,7 @@ package org.springframework.http;
 import java.io.Serializable;
 
 import org.springframework.lang.NonNull;
+import org.springframework.lang.Nullable;
 
 /**
  * Default implementation of {@link HttpStatusCode}.
@@ -89,7 +90,7 @@ final class DefaultHttpStatusCode
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		return (this == obj) || (obj instanceof HttpStatusCode that && this.value == that.value());
 	}
 

spring-web/src/main/java/org/springframework/http/HttpMethod.java

@@ -170,7 +170,7 @@ public final class HttpMethod implements Comparable<HttpMethod>, Serializable {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		return (this == obj) || (obj instanceof HttpMethod that && this.name.equals(that.name));
 	}
 

spring-web/src/main/java/org/springframework/web/cors/CorsConfiguration.java

@@ -743,7 +743,7 @@ public class CorsConfiguration {
 		}
 
 		@Override
-		public boolean equals(Object other) {
+		public boolean equals(@Nullable Object other) {
 			if (this == other) {
 				return true;
 			}

spring-web/src/test/java/org/springframework/http/codec/xml/Jaxb2XmlDecoderTests.java

@@ -41,6 +41,7 @@ import org.springframework.http.codec.xml.jaxb.XmlRootElementWithNameAndNamespac
 import org.springframework.http.codec.xml.jaxb.XmlType;
 import org.springframework.http.codec.xml.jaxb.XmlTypeWithName;
 import org.springframework.http.codec.xml.jaxb.XmlTypeWithNameAndNamespace;
+import org.springframework.lang.Nullable;
 import org.springframework.util.MimeType;
 import org.springframework.web.testfixture.xml.Pojo;
 
@@ -308,7 +309,7 @@ public class Jaxb2XmlDecoderTests extends AbstractLeakCheckingTests {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o) {
 				return true;
 			}

spring-web/src/test/java/org/springframework/http/converter/xml/Jaxb2CollectionHttpMessageConverterTests.java

@@ -35,6 +35,7 @@ import org.springframework.core.ParameterizedTypeReference;
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.Resource;
 import org.springframework.http.converter.HttpMessageNotReadableException;
+import org.springframework.lang.Nullable;
 import org.springframework.web.testfixture.http.MockHttpInputMessage;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -221,7 +222,7 @@ public class Jaxb2CollectionHttpMessageConverterTests {
 		public String external;
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o) {
 				return true;
 			}
@@ -252,7 +253,7 @@ public class Jaxb2CollectionHttpMessageConverterTests {
 		public String s = "Hello World";
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o) {
 				return true;
 			}

spring-web/src/testFixtures/java/org/springframework/web/testfixture/xml/Pojo.java

@@ -18,6 +18,8 @@ package org.springframework.web.testfixture.xml;
 
 import jakarta.xml.bind.annotation.XmlRootElement;
 
+import org.springframework.lang.Nullable;
+
 /**
  * @author Sebastien Deleuze
  */
@@ -53,7 +55,7 @@ public class Pojo {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 		if (this == o) {
 			return true;
 		}

spring-webflux/src/test/java/org/springframework/web/reactive/function/server/DispatcherHandlerIntegrationTests.java

@@ -31,6 +31,7 @@ import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
 import org.springframework.http.ResponseEntity;
 import org.springframework.http.server.reactive.HttpHandler;
+import org.springframework.lang.Nullable;
 import org.springframework.stereotype.Controller;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.ResponseBody;
@@ -266,7 +267,7 @@ class DispatcherHandlerIntegrationTests extends AbstractHttpHandlerIntegrationTe
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o) {
 				return true;
 			}

spring-webflux/src/test/java/org/springframework/web/reactive/function/server/PublisherHandlerFunctionIntegrationTests.java

@@ -27,6 +27,7 @@ import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.RequestEntity;
 import org.springframework.http.ResponseEntity;
+import org.springframework.lang.Nullable;
 import org.springframework.web.client.RestTemplate;
 import org.springframework.web.testfixture.http.server.reactive.bootstrap.HttpServer;
 
@@ -137,7 +138,7 @@ class PublisherHandlerFunctionIntegrationTests extends AbstractRouterFunctionInt
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o) {
 				return true;
 			}

spring-webflux/src/test/java/org/springframework/web/reactive/function/server/SseHandlerFunctionIntegrationTests.java

@@ -25,6 +25,7 @@ import reactor.test.StepVerifier;
 import org.springframework.core.ParameterizedTypeReference;
 import org.springframework.http.MediaType;
 import org.springframework.http.codec.ServerSentEvent;
+import org.springframework.lang.Nullable;
 import org.springframework.web.reactive.function.client.WebClient;
 import org.springframework.web.testfixture.http.server.reactive.bootstrap.HttpServer;
 
@@ -166,7 +167,7 @@ class SseHandlerFunctionIntegrationTests extends AbstractRouterFunctionIntegrati
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o) {
 				return true;
 			}

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/JacksonStreamingIntegrationTests.java

@@ -26,6 +26,7 @@ import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.http.MediaType;
 import org.springframework.http.server.reactive.HttpHandler;
+import org.springframework.lang.Nullable;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.RestController;
 import org.springframework.web.reactive.DispatcherHandler;
@@ -144,7 +145,7 @@ class JacksonStreamingIntegrationTests extends AbstractHttpHandlerIntegrationTes
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o) {
 				return true;
 			}

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/MessageReaderArgumentResolverTests.java

@@ -349,7 +349,7 @@ public class MessageReaderArgumentResolverTests {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o) {
 				return true;
 			}

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/RequestMappingMessageConversionIntegrationTests.java

@@ -49,6 +49,7 @@ import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
 import org.springframework.http.ResponseEntity;
 import org.springframework.http.codec.json.Jackson2JsonEncoder;
+import org.springframework.lang.Nullable;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.RequestBody;
@@ -703,7 +704,7 @@ class RequestMappingMessageConversionIntegrationTests extends AbstractRequestMap
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o) {
 				return true;
 			}

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/SseIntegrationTests.java

@@ -42,6 +42,7 @@ import org.springframework.http.client.reactive.JettyClientHttpConnector;
 import org.springframework.http.client.reactive.ReactorClientHttpConnector;
 import org.springframework.http.codec.ServerSentEvent;
 import org.springframework.http.server.reactive.HttpHandler;
+import org.springframework.lang.Nullable;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;
@@ -268,7 +269,7 @@ class SseIntegrationTests extends AbstractHttpHandlerIntegrationTests {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o) {
 				return true;
 			}

spring-webmvc/src/test/java/org/springframework/web/servlet/tags/form/ItemPet.java

@@ -18,6 +18,8 @@ package org.springframework.web.servlet.tags.form;
 
 import java.beans.PropertyEditorSupport;
 
+import org.springframework.lang.Nullable;
+
 /**
  * @author Juergen Hoeller
  */
@@ -42,7 +44,7 @@ public class ItemPet {
 	}
 
 	@Override
-	public boolean equals(Object other) {
+	public boolean equals(@Nullable Object other) {
 		if (this == other) {
 			return true;
 		}

spring-webmvc/src/test/java/org/springframework/web/servlet/tags/form/OptionTagTests.java

@@ -29,6 +29,7 @@ import org.junit.jupiter.api.Test;
 import org.springframework.beans.propertyeditors.StringArrayPropertyEditor;
 import org.springframework.beans.testfixture.beans.Colour;
 import org.springframework.beans.testfixture.beans.TestBean;
+import org.springframework.lang.Nullable;
 import org.springframework.util.StringUtils;
 import org.springframework.validation.BeanPropertyBindingResult;
 import org.springframework.web.servlet.support.BindStatus;
@@ -555,7 +556,7 @@ class OptionTagTests extends AbstractHtmlElementTagTests {
 		}
 
 		@Override
-		public boolean equals(Object obj) {
+		public boolean equals(@Nullable Object obj) {
 			if (obj instanceof RulesVariant other) {
 				return this.toId().equals(other.toId());
 			}

spring-websocket/src/test/java/org/springframework/web/socket/adapter/standard/ConvertingEncoderDecoderSupportTests.java

@@ -34,6 +34,7 @@ import org.springframework.core.convert.ConverterNotFoundException;
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.core.convert.support.DefaultConversionService;
 import org.springframework.core.convert.support.GenericConversionService;
+import org.springframework.lang.Nullable;
 import org.springframework.web.context.WebApplicationContext;
 import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
 import org.springframework.web.socket.ContextLoaderTestUtils;
@@ -232,11 +233,8 @@ public class ConvertingEncoderDecoderSupportTests {
 		}
 
 		@Override
-		public boolean equals(Object obj) {
-			if (obj instanceof MyType) {
-				return ((MyType)obj).value.equals(value);
-			}
-			return false;
+		public boolean equals(@Nullable Object obj) {
+			return (obj instanceof MyType that && this.value.equals(that.value));
 		}
 	}