I keep getting an error on while trying to create an App.

// Determine which fragment to display based on the item selected
    switch (item.getItemId()) {
        case R.id.nav_insert_meal:
            selectedFragment = new InsertMealFragment();
            break;
        case R.id.nav_view_meals:
            selectedFragment = new ViewMealsFragment();
            break;
        case R.id.nav_delete_meals:
            selectedFragment = new DeleteMealsFragment();
            break;
        default:
            selectedFragment = new HomeFragment();
            break;
    }>

The R.id.nav keeps saying a constant expression is required.

it is preventing me from running the App. Please help, how can I fix this?

I have tried all the ways to fix it and I am not sure how to correct this.