src/share/classes/javax/swing/plaf/basic/BasicMenuUI.java

*** 607,627 ****
  
              char key = Character.toLowerCase((char)menuItem.getMnemonic());
              MenuElement path[] = e.getPath();
              if (key == Character.toLowerCase(e.getKeyChar())) {
                  JPopupMenu popupMenu = ((JMenu)menuItem).getPopupMenu();
!                 ArrayList newList = new ArrayList(Arrays.asList(path));
                  newList.add(popupMenu);
                  MenuElement subs[] = popupMenu.getSubElements();
                  MenuElement sub =
                          BasicPopupMenuUI.findEnabledChild(subs, -1, true);
                  if(sub != null) {
                      newList.add(sub);
                  }
                  MenuSelectionManager manager = e.getMenuSelectionManager();
                  MenuElement newPath[] = new MenuElement[0];;
!                 newPath = (MenuElement[]) newList.toArray(newPath);
                  manager.setSelectedPath(newPath);
                  e.consume();
              }
          }
  
--- 607,627 ----
  
              char key = Character.toLowerCase((char)menuItem.getMnemonic());
              MenuElement path[] = e.getPath();
              if (key == Character.toLowerCase(e.getKeyChar())) {
                  JPopupMenu popupMenu = ((JMenu)menuItem).getPopupMenu();
!                 ArrayList<MenuElement> newList = new ArrayList<>(Arrays.asList(path));
                  newList.add(popupMenu);
                  MenuElement subs[] = popupMenu.getSubElements();
                  MenuElement sub =
                          BasicPopupMenuUI.findEnabledChild(subs, -1, true);
                  if(sub != null) {
                      newList.add(sub);
                  }
                  MenuSelectionManager manager = e.getMenuSelectionManager();
                  MenuElement newPath[] = new MenuElement[0];;
!                 newPath = newList.toArray(newPath);
                  manager.setSelectedPath(newPath);
                  e.consume();
              }
          }