Added subMenu function for class Menu with test

src/main/java/Application/Menu.java

@@ -1,11 +1,19 @@
 package Application;
 
+import java.util.ArrayList;
+
 public class Menu {
 
     private String name;
+    private ArrayList<Menu> subMenuList;
 
     public Menu(String name){
         setName(name);
+        subMenuList = new ArrayList<>();
+    }
+
+    public void addMenu(Menu menu){
+        subMenuList.add(menu);
     }
 
     public String getName() {
@@ -15,4 +23,8 @@ public class Menu {
     public void setName(String name) {
         this.name = name;
     }
+
+    public ArrayList<Menu> getSubMenuList() {
+        return this.subMenuList;
+    }
 }

src/test/java/Application/MenuTest.java

@@ -4,6 +4,8 @@ import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
+import java.util.ArrayList;
+
 import static org.junit.jupiter.api.Assertions.*;
 
 class MenuTest {
@@ -21,4 +23,16 @@ class MenuTest {
         Menu menu = new Menu("Item 1");
         assertTrue(menu.getName().equals("Item 1"));
     }
+
+    @Test
+    void testAddMenuFunction(){
+        ArrayList<Menu> menus = new ArrayList<>();
+        Menu menu1 = new Menu("Menu 1");
+        Menu menu2 = new Menu("Menu 2");
+        Menu menu1_1 = new Menu("Menu 1.1");
+        menu1.addMenu(menu1_1);
+        menus.add(menu1);
+        menus.add(menu2);
+        assertTrue(menus.get(0).equals(menu1) && menus.get(1).equals(menu2) && menus.get(0).getSubMenuList().get(0).equals(menu1_1));
+    }
 }