diff --git a/undertow/src/main/java/com/baeldung/undertow/ftp/FileServer.java b/undertow/src/main/java/com/baeldung/undertow/ftp/FileServer.java
index 90cad9ebbd..f5cdb827a6 100644
--- a/undertow/src/main/java/com/baeldung/undertow/ftp/FileServer.java
+++ b/undertow/src/main/java/com/baeldung/undertow/ftp/FileServer.java
@@ -1,19 +1,19 @@
 package com.baeldung.undertow.ftp;
 
-import java.nio.file.Paths;
-
 import io.undertow.Undertow;
 import io.undertow.server.handlers.resource.PathResourceManager;
 
+import java.nio.file.Paths;
+
 import static io.undertow.Handlers.resource;
 
 public class FileServer {
 
     public static void main(String[] args) {
         Undertow server = Undertow.builder().addHttpListener(8080, "localhost")
-                .setHandler(resource(new PathResourceManager(Paths.get(System.getProperty("user.home")), 100))
-                        .setDirectoryListingEnabled(true))
-                .build();
+          .setHandler(resource(new PathResourceManager(Paths.get(System.getProperty("user.home")), 100))
+            .setDirectoryListingEnabled(true))
+          .build();
         server.start();
     }
 
diff --git a/undertow/src/main/java/com/baeldung/undertow/secure/CustomIdentityManager.java b/undertow/src/main/java/com/baeldung/undertow/secure/CustomIdentityManager.java
index 16231f036d..491941261a 100644
--- a/undertow/src/main/java/com/baeldung/undertow/secure/CustomIdentityManager.java
+++ b/undertow/src/main/java/com/baeldung/undertow/secure/CustomIdentityManager.java
@@ -54,12 +54,7 @@ public class CustomIdentityManager implements IdentityManager {
 
                 private static final long serialVersionUID = 1L;
 
-                private final Principal principal = new Principal() {
-                    @Override
-                    public String getName() {
-                        return id;
-                    }
-                };
+                private final Principal principal = () -> id;
 
                 @Override
                 public Principal getPrincipal() {
diff --git a/undertow/src/main/java/com/baeldung/undertow/secure/SecureServer.java b/undertow/src/main/java/com/baeldung/undertow/secure/SecureServer.java
index 9997883da6..6532c3ed7c 100644
--- a/undertow/src/main/java/com/baeldung/undertow/secure/SecureServer.java
+++ b/undertow/src/main/java/com/baeldung/undertow/secure/SecureServer.java
@@ -1,10 +1,5 @@
 package com.baeldung.undertow.secure;
 
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-
 import io.undertow.Undertow;
 import io.undertow.io.IoCallback;
 import io.undertow.security.api.AuthenticationMechanism;
@@ -19,6 +14,11 @@ import io.undertow.security.impl.BasicAuthenticationMechanism;
 import io.undertow.server.HttpHandler;
 import io.undertow.server.HttpServerExchange;
 
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
 public class SecureServer {
 
     public static void main(String[] args) {
@@ -28,16 +28,16 @@ public class SecureServer {
 
         final IdentityManager idm = new CustomIdentityManager(users);
 
-        Undertow server = Undertow.builder().addHttpListener(8080, "localhost").setHandler(addSecurity((exchange) -> {
-            setExchange(exchange);
-        }, idm)).build();
+        Undertow server = Undertow.builder()
+          .addHttpListener(8080, "localhost")
+          .setHandler(addSecurity(SecureServer::setExchange, idm)).build();
 
         server.start();
     }
 
     private static void setExchange(HttpServerExchange exchange) {
         final SecurityContext context = exchange.getSecurityContext();
-        exchange.getResponseSender().send("Hello " + context.getAuthenticatedAccount().getPrincipal().getName(),IoCallback.END_EXCHANGE);
+        exchange.getResponseSender().send("Hello " + context.getAuthenticatedAccount().getPrincipal().getName(), IoCallback.END_EXCHANGE);
     }
 
     private static HttpHandler addSecurity(final HttpHandler toWrap, final IdentityManager identityManager) {
@@ -45,7 +45,7 @@ public class SecureServer {
         handler = new AuthenticationCallHandler(handler);
         handler = new AuthenticationConstraintHandler(handler);
         final List<AuthenticationMechanism> mechanisms = Collections
-                .<AuthenticationMechanism> singletonList(new BasicAuthenticationMechanism("Baeldung_Realm"));
+          .singletonList(new BasicAuthenticationMechanism("Baeldung_Realm"));
         handler = new AuthenticationMechanismsHandler(handler, mechanisms);
         handler = new SecurityInitialHandler(AuthenticationMode.PRO_ACTIVE, identityManager, handler);
         return handler;