GayanM’s gists

GayanM / ProductResource.java

Created September 21, 2022 07:36

Filter products by category and price range

	@RequestMapping("")
	public List<Product> filterProducts(@Param("category") final Optional<String> category,
	@Param("lower-price-limit") final Optional<Double> lowerLimitPrice,
	@RequestParam("upper-price-limit") final Optional<Double> upperLimitPrice ) {


	return productRepos.findAll().stream().
	filter(p -> {
	if (category.isEmpty()) {
	return true;

GayanM / OrderResource.java

Created September 25, 2022 04:09

Get orders contains given product category

	@RequestMapping("")
	public List<Order> getOrdersByProductCategory (@RequestParam("category") final Optional<String> category) {
	return orderRepo.findAll().stream().
	filter(o -> o.getProducts().stream().anyMatch(p -> {
	if (category.isEmpty()) {
	return true;
	}
	return category.get().equalsIgnoreCase(p.getCategory());
	})).
	map(o -> new Order(o.getId(), o.getOrderDate(), o.getDeliveryDate(), o.getStatus())).

GayanM / ProductResourceDiscount.java

Created September 25, 2022 04:16

Ex-3:Obtain a list of product with given category and then apply 10% discount

	@RequestMapping("/discount")
	public List<Product> applyDiscountOnCategory(@RequestParam("category") final Optional<String> category,
	@RequestParam("discount") final Optional<Double> discount) {
	return productRepos.findAll().stream().
	filter(p -> {
	if (category.isEmpty()) {
	return true;
	}
	return category.get().equalsIgnoreCase(p.getCategory());
	}).map(p -> {

GayanM / ProductsByCustomerTier.java

Created September 25, 2022 04:22

Ex-4: Obtain a list of products based on customer tier and date range

	@RequestMapping("/customer-tier")
	public List<Product> getProductsByCustomerTier (@RequestParam("tier") final Optional<Integer> tier,
	@RequestParam("start-date") final Optional<String> startDate,
	@RequestParam("end-date") final Optional<String> endDate) {
	DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
	return orderRepo.findAll().stream().
	filter(o -> {
	if (tier.isEmpty()) {
	return true;
	}

GayanM / CheapestProduct.java

Created September 25, 2022 04:28

Ex-5: Get the cheapest products by category

	@RequestMapping("/cheapest")
	public Optional<Product> getCheapestProductByCategory(@RequestParam("category") final Optional<String> category) {
	return productRepos.findAll().stream().filter(p -> {
	if (category.isEmpty()) {
	return true;
	}
	return category.get().equalsIgnoreCase(p.getCategory());
	}).min(Comparator.comparing(com.mycompany.functional.programming.exercises.models.Product::getPrice)).map(p ->
	new Product(p.getId(), p.getName(), p.getPrice(), p.getCategory()));
	}

GayanM / RecentOrders.java

Created September 25, 2022 10:10

Get the 3 most recent placed order

	@RequestMapping("/recent")
	public List<Order> getRecentOrders (@RequestParam("limit") final Optional<Long> limit) {
	return orderRepo.findAll().stream().
	sorted(Comparator.
	comparing(com.mycompany.functional.programming.exercises.models.Order::getOrderDate).
	reversed()).limit(limit.get()).map(o -> new Order(o.getId(), o.getOrderDate(),
	o.getDeliveryDate(), o.getStatus())).collect(Collectors.toList());
	}

GayanM / LogOrders.java

Created September 25, 2022 10:16

Get a list of orders which were ordered on 15-Mar-2021, log the order records to the console and then return its product list


	@RequestMapping("/log-orders")
	public List<Product> logOrdersOnGivenDateAndReturnProducts(@RequestParam("date") final Optional<String> date) {
	DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
	return orderRepo.findAll().stream()
	.filter(o -> o.getOrderDate().isEqual(LocalDate.parse(date.get(), formatter)))
	.peek(o -> System.out.println(o.toString()))
	.flatMap(o -> o.getProducts().stream())
	.distinct().map(p -> new Product(p.getId(), p.getName(), p.getPrice(), p.getCategory()))
	.collect(Collectors.toList());

GayanM / LumpSumOfOrders.java

Created September 25, 2022 10:21

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

	@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();

GayanM / AvgPayment.java

Created September 25, 2022 10:25

Calculate order average payment placed on 14-Mar-2021:Answ=287.604

	@RequestMapping("/avg-payment")
	public Double getAvgPayment(@RequestParam("date") final Optional<String> date) {
	DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
	return orderRepo.findAll().stream().filter(o -> o.getOrderDate().isEqual(LocalDate.
	parse(date.get(), formatter))).flatMap(o -> o.getProducts().stream()).mapToDouble(p ->
	p.getPrice()).average().getAsDouble();
	}

GayanM / Statistics.java

Created September 25, 2022 10:28

Obtain a collection of statistic figures (i.e. sum, average, max, min, count) for all products of given category

	@RequestMapping("/statistics")
	public DoubleSummaryStatistics getStatistics(@RequestParam("category") final Optional<String> category) {
	return productRepos.findAll().stream().filter(p -> category.get().equalsIgnoreCase(p.getCategory())).
	mapToDouble(p -> p.getPrice()).summaryStatistics();
	}

Gayan GayanM