Implement micro performance optimizations

- ClassUtils.isAssignable(): Avoid Map lookup when the type is not a
  primitive.

- AnnotationsScanner: Perform low cost array length check before String
  comparisons.

- BeanFactoryUtils: Use char comparison instead of String comparison.
  The bean factory prefix is '&', so we can use a char comparison
  instead of more heavyweight String.startsWith("&").

- AbstractBeanFactory.getMergedBeanDefinition(): Perform the low cost
  check first. Map lookup, while cheap, is still more expensive than
  instanceof.

Closes gh-34717

Signed-off-by: Olivier Bourgain <olivierbourgain02@gmail.com>

spring-beans/src/main/java/org/springframework/beans/factory/BeanFactoryUtils.java

@@ -63,6 +63,13 @@ public abstract class BeanFactoryUtils {
 	 */
 	private static final Map<String, String> transformedBeanNameCache = new ConcurrentHashMap<>();
 
+	/**
+	 * Used to dereference a {@link FactoryBean} instance and distinguish it from
+	 * beans <i>created</i> by the FactoryBean. For example, if the bean named
+	 * {@code myJndiObject} is a FactoryBean, getting {@code &myJndiObject}
+	 * will return the factory, not the instance returned by the factory.
+	 */
+	private static final char FACTORY_BEAN_PREFIX = BeanFactory.FACTORY_BEAN_PREFIX.charAt(0);
 
 	/**
 	 * Return whether the given name is a factory dereference
@@ -72,7 +79,7 @@ public abstract class BeanFactoryUtils {
 	 * @see BeanFactory#FACTORY_BEAN_PREFIX
 	 */
 	public static boolean isFactoryDereference(@Nullable String name) {
-		return (name != null && name.startsWith(BeanFactory.FACTORY_BEAN_PREFIX));
+		return (name != null && !name.isEmpty()	&& name.charAt(0) == FACTORY_BEAN_PREFIX);
 	}
 
 	/**
@@ -84,14 +91,14 @@ public abstract class BeanFactoryUtils {
 	 */
 	public static String transformedBeanName(String name) {
 		Assert.notNull(name, "'name' must not be null");
-		if (!name.startsWith(BeanFactory.FACTORY_BEAN_PREFIX)) {
+		if (!isFactoryDereference(name)) {
 			return name;
 		}
 		return transformedBeanNameCache.computeIfAbsent(name, beanName -> {
 			do {
 				beanName = beanName.substring(BeanFactory.FACTORY_BEAN_PREFIX.length());
 			}
-			while (beanName.startsWith(BeanFactory.FACTORY_BEAN_PREFIX));
+			while (isFactoryDereference(beanName));
 			return beanName;
 		});
 	}

spring-beans/src/main/java/org/springframework/beans/factory/support/AbstractBeanFactory.java

@@ -1153,7 +1153,7 @@ public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport imp
 	public BeanDefinition getMergedBeanDefinition(String name) throws BeansException {
 		String beanName = transformedBeanName(name);
 		// Efficiently check whether bean definition exists in this factory.
-		if (!containsBeanDefinition(beanName) && getParentBeanFactory() instanceof ConfigurableBeanFactory parent) {
+		if (getParentBeanFactory() instanceof ConfigurableBeanFactory parent && !containsBeanDefinition(beanName)) {
 			return parent.getMergedBeanDefinition(beanName);
 		}
 		// Resolve merged bean definition locally.

spring-core/src/main/java/org/springframework/core/annotation/AnnotationsScanner.java

@@ -355,6 +355,7 @@ abstract class AnnotationsScanner {
 
 	private static boolean isOverride(Method rootMethod, Method candidateMethod) {
 		return (!Modifier.isPrivate(candidateMethod.getModifiers()) &&
+				candidateMethod.getParameterCount() == rootMethod.getParameterCount() &&
 				candidateMethod.getName().equals(rootMethod.getName()) &&
 				hasSameParameterTypes(rootMethod, candidateMethod));
 	}

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

@@ -637,10 +637,11 @@ public abstract class ClassUtils {
 			Class<?> resolvedPrimitive = primitiveWrapperTypeMap.get(rhsType);
 			return (lhsType == resolvedPrimitive);
 		}
-		else {
+		else if (rhsType.isPrimitive()) {
 			Class<?> resolvedWrapper = primitiveTypeToWrapperMap.get(rhsType);
 			return (resolvedWrapper != null && lhsType.isAssignableFrom(resolvedWrapper));
 		}
+		return false;
 	}
 
 	/**