diff --git a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/util/LambdaSafe.java b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/util/LambdaSafe.java
index 04bd7c8430..ad4cf2e092 100644
--- a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/util/LambdaSafe.java
+++ b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/util/LambdaSafe.java
@@ -286,12 +286,11 @@ public final class LambdaSafe {
 		 * @param invoker the invoker used to invoke the callback
 		 */
 		public void invoke(Consumer<C> invoker) {
-			Function<C, InvocationResult<Void>> mapper = (callbackInstance) -> invoke(
-					callbackInstance, () -> {
-						invoker.accept(callbackInstance);
-						return null;
-					});
-			this.callbackInstances.stream().map(mapper).forEach((result) -> {
+			this.callbackInstances.forEach((callbackInstance) -> {
+				invoke(callbackInstance, () -> {
+					invoker.accept(callbackInstance);
+					return null;
+				});
 			});
 		}
 
diff --git a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/undertow/UndertowServletWebServerFactory.java b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/undertow/UndertowServletWebServerFactory.java
index dcd0e22dc2..46aa264046 100644
--- a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/undertow/UndertowServletWebServerFactory.java
+++ b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/undertow/UndertowServletWebServerFactory.java
@@ -354,11 +354,13 @@ public class UndertowServletWebServerFactory extends AbstractServletWebServerFac
 		File docBase = getCanonicalDocumentRoot(root);
 		List<URL> metaInfResourceUrls = getUrlsOfJarsWithMetaInfResources();
 		List<URL> resourceJarUrls = new ArrayList<>();
-		List<ResourceManager> resourceManagers = new ArrayList<>();
-		ResourceManager rootResourceManager = (docBase.isDirectory()
+		List<ResourceManager> managers = new ArrayList<>();
+		ResourceManager rootManager = (docBase.isDirectory()
 				? new FileResourceManager(docBase, 0) : new JarResourceManager(docBase));
-		resourceManagers.add(root == null ? rootResourceManager
-				: new LoaderHidingResourceManager(rootResourceManager));
+		if (root != null) {
+			rootManager = new LoaderHidingResourceManager(rootManager);
+		}
+		managers.add(rootManager);
 		for (URL url : metaInfResourceUrls) {
 			if ("file".equals(url.getProtocol())) {
 				try {
@@ -367,7 +369,7 @@ public class UndertowServletWebServerFactory extends AbstractServletWebServerFac
 						resourceJarUrls.add(new URL("jar:" + url + "!/"));
 					}
 					else {
-						resourceManagers.add(new FileResourceManager(
+						managers.add(new FileResourceManager(
 								new File(file, "META-INF/resources"), 0));
 					}
 				}
@@ -379,9 +381,8 @@ public class UndertowServletWebServerFactory extends AbstractServletWebServerFac
 				resourceJarUrls.add(url);
 			}
 		}
-		resourceManagers.add(new MetaInfResourcesResourceManager(resourceJarUrls));
-		return new CompositeResourceManager(
-				resourceManagers.toArray(new ResourceManager[0]));
+		managers.add(new MetaInfResourcesResourceManager(resourceJarUrls));
+		return new CompositeResourceManager(managers.toArray(new ResourceManager[0]));
 	}
 
 	private File getCanonicalDocumentRoot(File docBase) {