Fix equals nullability annotations for jspecify compliance

In this commit, we added `@Nullable` to equals methods of classes that
support `jspecify` for consistency with other Spring projects and to
avoid bugs that caused other Spring projects to do this natively.

Closes: gh-18929, gh-18927

Signed-off-by: Andrey Litvitski <andrey1010102008@gmail.com>

core/src/main/java/org/springframework/security/authentication/AbstractAuthenticationToken.java

@@ -132,7 +132,7 @@ public abstract class AbstractAuthenticationToken implements Authentication, Cre
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (!(obj instanceof AbstractAuthenticationToken test)) {
 			return false;
 		}

core/src/main/java/org/springframework/security/authentication/AnonymousAuthenticationToken.java

@@ -19,6 +19,8 @@ package org.springframework.security.authentication;
 import java.io.Serializable;
 import java.util.Collection;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.security.core.GrantedAuthority;
 import org.springframework.util.Assert;
 
@@ -70,7 +72,7 @@ public class AnonymousAuthenticationToken extends AbstractAuthenticationToken im
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (!super.equals(obj)) {
 			return false;
 		}

core/src/main/java/org/springframework/security/authentication/RememberMeAuthenticationToken.java

@@ -103,7 +103,7 @@ public class RememberMeAuthenticationToken extends AbstractAuthenticationToken {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (!super.equals(obj)) {
 			return false;
 		}

core/src/main/java/org/springframework/security/authentication/jaas/JaasGrantedAuthority.java

@@ -18,6 +18,8 @@ package org.springframework.security.authentication.jaas;
 
 import java.security.Principal;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.security.core.GrantedAuthority;
 import org.springframework.util.Assert;
 
@@ -53,7 +55,7 @@ public final class JaasGrantedAuthority implements GrantedAuthority {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (this == obj) {
 			return true;
 		}

core/src/main/java/org/springframework/security/authorization/RequiredFactor.java

@@ -71,7 +71,7 @@ public final class RequiredFactor {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 		if (!(o instanceof RequiredFactor that)) {
 			return false;
 		}

core/src/main/java/org/springframework/security/authorization/RequiredFactorError.java

@@ -18,6 +18,8 @@ package org.springframework.security.authorization;
 
 import java.util.Objects;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.security.core.authority.FactorGrantedAuthority;
 import org.springframework.util.Assert;
 
@@ -68,7 +70,7 @@ public class RequiredFactorError {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 		if (o == null || getClass() != o.getClass()) {
 			return false;
 		}

core/src/main/java/org/springframework/security/core/ComparableVersion.java

@@ -143,7 +143,7 @@ class ComparableVersion implements Comparable<ComparableVersion> {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o) {
 				return true;
 			}
@@ -208,7 +208,7 @@ class ComparableVersion implements Comparable<ComparableVersion> {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o) {
 				return true;
 			}
@@ -271,7 +271,7 @@ class ComparableVersion implements Comparable<ComparableVersion> {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o) {
 				return true;
 			}
@@ -379,7 +379,7 @@ class ComparableVersion implements Comparable<ComparableVersion> {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o) {
 				return true;
 			}
@@ -607,7 +607,7 @@ class ComparableVersion implements Comparable<ComparableVersion> {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 		return (o instanceof ComparableVersion) && items.equals(((ComparableVersion) o).items);
 	}
 

core/src/main/java/org/springframework/security/core/authority/FactorGrantedAuthority.java

@@ -150,7 +150,7 @@ public final class FactorGrantedAuthority implements GrantedAuthority {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (this == obj) {
 			return true;
 		}

core/src/main/java/org/springframework/security/core/authority/SimpleGrantedAuthority.java

@@ -16,6 +16,8 @@
 
 package org.springframework.security.core.authority;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.security.core.GrantedAuthority;
 import org.springframework.util.Assert;
 
@@ -51,7 +53,7 @@ public final class SimpleGrantedAuthority implements GrantedAuthority {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (this == obj) {
 			return true;
 		}

core/src/main/java/org/springframework/security/core/context/SecurityContextImpl.java

@@ -42,7 +42,7 @@ public class SecurityContextImpl implements SecurityContext {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (obj instanceof SecurityContextImpl other) {
 			if ((this.getAuthentication() == null) && (other.getAuthentication() == null)) {
 				return true;

core/src/main/java/org/springframework/security/core/token/DefaultToken.java

@@ -18,6 +18,8 @@ package org.springframework.security.core.token;
 
 import java.util.Date;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.util.Assert;
 
 /**
@@ -58,7 +60,7 @@ public class DefaultToken implements Token {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (obj instanceof DefaultToken rhs) {
 			return this.key.equals(rhs.key) && this.keyCreationTime == rhs.keyCreationTime
 					&& this.extendedInformation.equals(rhs.extendedInformation);

core/src/main/java/org/springframework/security/core/userdetails/User.java

@@ -177,7 +177,7 @@ public class User implements UserDetails, CredentialsContainer {
 	 * the same principal.
 	 */
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (obj instanceof User user) {
 			return this.username.equals(user.getUsername());
 		}