public Function<Order, Boolean> isBigOrder() {

        Function<Order, Optional<Long>> sum = a -> a.getProducts()
                .stream()
                .map(P -> P.getPrice())
                .reduce((p1,p2)->p1+p2);

        Predicate <Optional<Long>> isBig =  x -> x.get() > 1000 ;

        return ????;
    }

enum OrderState {CONFIRMED, PAID, WAREHOUSE_PROCESSED, READY_TO_SEND, DELIVERED }

   enum ProductType { NORMAL, BREAKABLE, PERISHABLE }




public class Product {
    private String code;
    private String title;
    private long price;
    private ProductState state;
    private ProductType type;

    //all fields have getter and setter

    public Product price(long price) {
        this.price = price;
        return this;
    }
}




public class Order {

    private String code;
    private long price;
    private String buyyer;
    private OrderState state;
    private List<Product> products = new ArrayList<>();

    //all fields have getter and setter

    public Order price(long price) {
        this.price = price;
        return this;
    }

    public Order product(Product product) {
        if (products == null) {
            products = new ArrayList<>();
        }
        products.add(product);
        return this;
    }

}