diff -r f7433671fec5 -r 1c62c6009161 src/main/java/de/uapcore/sudoku/MainMenu.java
--- a/src/main/java/de/uapcore/sudoku/MainMenu.java	Sat Jul 25 15:56:48 2020 +0200
+++ b/src/main/java/de/uapcore/sudoku/MainMenu.java	Mon Jul 27 10:56:17 2020 +0200
@@ -33,8 +33,8 @@
  */
 public class MainMenu {
     
-    private ActionHandler handler;
-    private JMenuBar menuBar;
+    private final ActionHandler handler;
+    private final JMenuBar menuBar;
     
     public MainMenu(ActionHandler h) {
         handler = h;