    @Test
    public void checkOut() throws Exception {

       /* Inventory[] inventory = new Inventory[2];
        Product product1 = new Product();
        Product product2 = new Product();

        Map<String, Long> inventoryItems = Arrays.stream(inventory)
                .map(inv -> inv.getProduct().getProductId())
                .collect(groupingBy(Function.identity(), counting()));*/

    }