diff --git a/spring-core/src/main/java/org/springframework/core/io/support/PropertySourceProcessor.java b/spring-core/src/main/java/org/springframework/core/io/support/PropertySourceProcessor.java
index df19941a0b..d24acd6327 100644
--- a/spring-core/src/main/java/org/springframework/core/io/support/PropertySourceProcessor.java
+++ b/spring-core/src/main/java/org/springframework/core/io/support/PropertySourceProcessor.java
@@ -49,22 +49,24 @@ import org.springframework.util.ReflectionUtils;
  */
 public class PropertySourceProcessor {
 
-	private static final PropertySourceFactory DEFAULT_PROPERTY_SOURCE_FACTORY = new DefaultPropertySourceFactory();
+	private static final PropertySourceFactory defaultPropertySourceFactory = new DefaultPropertySourceFactory();
 
 	private static final Log logger = LogFactory.getLog(PropertySourceProcessor.class);
 
+
 	private final ConfigurableEnvironment environment;
 
 	private final ResourceLoader resourceLoader;
 
-	private final List<String> propertySourceNames;
+	private final List<String> propertySourceNames = new ArrayList<>();
+
 
 	public PropertySourceProcessor(ConfigurableEnvironment environment, ResourceLoader resourceLoader) {
 		this.environment = environment;
 		this.resourceLoader = resourceLoader;
-		this.propertySourceNames = new ArrayList<>();
 	}
 
+
 	/**
 	 * Process the specified {@link PropertySourceDescriptor} against the
 	 * environment managed by this instance.
@@ -78,7 +80,7 @@ public class PropertySourceProcessor {
 		Assert.isTrue(locations.size() > 0, "At least one @PropertySource(value) location is required");
 		boolean ignoreResourceNotFound = descriptor.ignoreResourceNotFound();
 		PropertySourceFactory factory = (descriptor.propertySourceFactory() != null ?
-				instantiateClass(descriptor.propertySourceFactory()) : DEFAULT_PROPERTY_SOURCE_FACTORY);
+				instantiateClass(descriptor.propertySourceFactory()) : defaultPropertySourceFactory);
 
 		for (String location : locations) {
 			try {
@@ -100,13 +102,13 @@ public class PropertySourceProcessor {
 		}
 	}
 
-	private void addPropertySource(org.springframework.core.env.PropertySource<?> propertySource) {
+	private void addPropertySource(PropertySource<?> propertySource) {
 		String name = propertySource.getName();
 		MutablePropertySources propertySources = this.environment.getPropertySources();
 
 		if (this.propertySourceNames.contains(name)) {
 			// We've already added a version, we need to extend it
-			org.springframework.core.env.PropertySource<?> existing = propertySources.get(name);
+			PropertySource<?> existing = propertySources.get(name);
 			if (existing != null) {
 				PropertySource<?> newSource = (propertySource instanceof ResourcePropertySource rps ?
 						rps.withResourceName() : propertySource);
@@ -136,7 +138,8 @@ public class PropertySourceProcessor {
 		this.propertySourceNames.add(name);
 	}
 
-	private PropertySourceFactory instantiateClass(Class<? extends PropertySourceFactory> type) {
+
+	private static PropertySourceFactory instantiateClass(Class<? extends PropertySourceFactory> type) {
 		try {
 			Constructor<? extends PropertySourceFactory> constructor = type.getDeclaredConstructor();
 			ReflectionUtils.makeAccessible(constructor);