How to refer to sub-item of menu menuItem?

Question

Android

How can I refer to the submenu menuItem?
I tried to assign menuItem id variable in onCreateOptionsMenu:

@Override
    public boolean onCreateOptionsMenu(Menu menu) {
       getMenuInflater().inflate(R.menu.menu, menu);
       menuItem = menu.getItem(0);                           // Первый способ
       menuItem = menu.getItem(R.id.addElement);   // Второй способ
       menuItem = menu.findItem(R.id.addElement);  // Третий способ
       
       return super.onCreateOptionsMenu(menu);
    }

I will need to refer to this variable in onCreate