Nullability refinements

See gh-32475

spring-core-test/src/main/java/org/springframework/core/test/io/support/MockSpringFactoriesLoader.java

@@ -67,6 +67,7 @@ public class MockSpringFactoriesLoader extends SpringFactoriesLoader {
 
 
 	@Override
+	@Nullable
 	@SuppressWarnings("unchecked")
 	protected <T> T instantiateFactory(String implementationName, Class<T> type,
 			@Nullable ArgumentResolver argumentResolver, FailureHandler failureHandler) {

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

@@ -94,6 +94,7 @@ public abstract class ValueCodeGeneratorDelegates {
 
 		@Override
 		@SuppressWarnings("unchecked")
+		@Nullable
 		public CodeBlock generateCode(ValueCodeGenerator valueCodeGenerator, Object value) {
 			if (this.collectionType.isInstance(value)) {
 				T collection = (T) value;
@@ -135,6 +136,7 @@ public abstract class ValueCodeGeneratorDelegates {
 		private static final CodeBlock EMPTY_RESULT = CodeBlock.of("$T.emptyMap()", Collections.class);
 
 		@Override
+		@Nullable
 		public CodeBlock generateCode(ValueCodeGenerator valueCodeGenerator, Object value) {
 			if (value instanceof Map<?, ?> map) {
 				if (map.isEmpty()) {

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

@@ -18,6 +18,7 @@ package org.springframework.aot.hint.support;
 
 import org.springframework.aot.hint.RuntimeHints;
 import org.springframework.aot.hint.RuntimeHintsRegistrar;
+import org.springframework.lang.Nullable;
 
 /**
  * {@link RuntimeHintsRegistrar} to register hints for {@link org.springframework.core.SpringProperties}.
@@ -28,7 +29,7 @@ import org.springframework.aot.hint.RuntimeHintsRegistrar;
 class SpringPropertiesRuntimeHints implements RuntimeHintsRegistrar {
 
 		@Override
-		public void registerHints(RuntimeHints hints, ClassLoader classLoader) {
+		public void registerHints(RuntimeHints hints, @Nullable ClassLoader classLoader) {
 			hints.resources().registerPattern("spring.properties");
 		}
 }

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

@@ -96,6 +96,7 @@ final class UnmodifiableMultiValueMap<K,V> implements MultiValueMap<K,V>, Serial
 	}
 
 	@Override
+	@Nullable
 	public V getFirst(K key) {
 		return this.delegate.getFirst(key);
 	}