Calculate total lump sum of all orders placed in Feb 2021:Answ=11995.36

LumpSumOfOrders.java

    @RequestMapping("/lump-sum")
    public Double lumpSumOfOrders (@RequestParam("month") final int month) {
        return orderRepo.findAll()
                .stream()
                .filter(o -> o.getOrderDate().compareTo(LocalDate.of(2021, month, 1)) >= 0)
                .filter(o -> o.getOrderDate().compareTo(LocalDate.of(2021, month + 1, 1)) < 0)
                .flatMap(o -> o.getProducts().stream())
                .mapToDouble(p -> p.getPrice())
                .sum();

    }