Introduce ObjectUtils#nullSafeHash(Object... element)

This commit deprecates the various nullSafeHashCode methods taking array
types as they are superseded by Arrays.hashCode now. This means that
the now only remaining nullSafeHashCode method does not trigger a
warning only if the target type is not an array. At the same time, there
are multiple use of this method on several elements, handling the
accumulation of hash codes.

For that reason, this commit also introduces a nullSafeHash that takes
an array of elements. The only difference between Objects.hash is that
this method handles arrays.

The codebase has been reviewed to use any of those two methods when it
is possible.

Closes gh-29051

spring-context/src/main/java/org/springframework/context/event/AbstractApplicationEventMulticaster.java

@@ -21,6 +21,7 @@ import java.util.Collection;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.Predicate;
@@ -404,7 +405,7 @@ public abstract class AbstractApplicationEventMulticaster
 
 		@Override
 		public int hashCode() {
-			return this.eventType.hashCode() * 29 + ObjectUtils.nullSafeHashCode(this.sourceType);
+			return Objects.hash(this.eventType, this.sourceType);
 		}
 
 		@Override

spring-context/src/main/java/org/springframework/context/support/ApplicationListenerDetector.java

@@ -17,6 +17,7 @@
 package org.springframework.context.support;
 
 import java.util.Map;
+import java.util.Objects;
 import java.util.concurrent.ConcurrentHashMap;
 
 import org.apache.commons.logging.Log;
@@ -28,7 +29,6 @@ import org.springframework.beans.factory.support.RootBeanDefinition;
 import org.springframework.context.ApplicationListener;
 import org.springframework.context.event.ApplicationEventMulticaster;
 import org.springframework.lang.Nullable;
-import org.springframework.util.ObjectUtils;
 
 /**
  * {@code BeanPostProcessor} that detects beans which implement the {@code ApplicationListener}
@@ -120,7 +120,7 @@ class ApplicationListenerDetector implements DestructionAwareBeanPostProcessor,
 
 	@Override
 	public int hashCode() {
-		return ObjectUtils.nullSafeHashCode(this.applicationContext);
+		return Objects.hashCode(this.applicationContext);
 	}
 
 }

spring-context/src/main/java/org/springframework/context/support/DefaultMessageSourceResolvable.java

@@ -179,10 +179,7 @@ public class DefaultMessageSourceResolvable implements MessageSourceResolvable,
 
 	@Override
 	public int hashCode() {
-		int hashCode = ObjectUtils.nullSafeHashCode(getCodes());
-		hashCode = 29 * hashCode + ObjectUtils.nullSafeHashCode(getArguments());
-		hashCode = 29 * hashCode + ObjectUtils.nullSafeHashCode(getDefaultMessage());
-		return hashCode;
+		return ObjectUtils.nullSafeHash(getCode(), getArguments(), getDefaultMessage());
 	}
 
 }

spring-context/src/main/java/org/springframework/jmx/support/NotificationListenerHolder.java

@@ -167,11 +167,8 @@ public class NotificationListenerHolder {
 
 	@Override
 	public int hashCode() {
-		int hashCode = ObjectUtils.nullSafeHashCode(this.notificationListener);
-		hashCode = 29 * hashCode + ObjectUtils.nullSafeHashCode(this.notificationFilter);
-		hashCode = 29 * hashCode + ObjectUtils.nullSafeHashCode(this.handback);
-		hashCode = 29 * hashCode + ObjectUtils.nullSafeHashCode(this.mappedObjectNames);
-		return hashCode;
+		return ObjectUtils.nullSafeHash(this.notificationListener, this.notificationFilter,
+				this.handback, this.mappedObjectNames);
 	}
 
 }