Price Categorizer with Discounts

import java.text.DecimalFormat;

import java.util.List;

import java.util.ArrayList;

import java.util.Map;

import java.util.TreeMap;

import java.util.Random;

import java.util.stream.Stream;

import java.util.stream.Collectors;

class Main {

private final static List<String> CATEGORIES = List.of("Cheap", "Moderate", "Expensive");

public static void main(String[] args) {

List<Item> items = getItemsList();

Map<String, List<Item>> itemsByName = getItemsByName(items);

Map<String, List<Item>> itemsByCategories = categorizeItems(itemsByName);

// itemsByCategories.entrySet().forEach(item -> System.out.println(item.getKey() + ": " + item.getValue().stream().map(i -> i.getName() + ": " + i.getPrice()).collect(Collectors.joining(", "))));

printReport(itemsByCategories);

}

private static List<Item> getItemsList() {

// Data generation

final int minPrice = 1;

final int maxPrice = 1000;

Random rand = new Random();

return List.of("Mouse", "Keyboard", "Battery", "Laptop", "Pad Mouse", "Ethernet Cable", "Notebook", "Pen")

.stream()

.flatMap(item -> Stream.generate(() -> item).limit(rand.nextInt(20 - 1) + 1))

.map(product -> new Item(product, Math.round(rand.nextDouble(minPrice, maxPrice) * 100.0) / 100.0))

.toList();

}

private static Map<String, List<Item>> getItemsByName(List<Item> items) {

return items.stream()

.collect(Collectors.groupingBy(item -> item.getName(), TreeMap::new, Collectors.toList()));

}

private static Map<String, List<Item>> categorizeItems(Map<String, List<Item>> items) {

Map<String, List<Item>> itemsByCategories = Map.of("Cheap", new ArrayList<Item>(), "Moderate", new ArrayList<Item>(), "Expensive", new ArrayList<Item>());

items.values().stream().flatMap(List::stream).forEach(item -> {

if (item.getPrice() < 20.0) {

var cheap = itemsByCategories.get("Cheap");

cheap.add(item);

} else if (item.getPrice() >= 20 && item.getPrice() <= 100) {

var moderate = itemsByCategories.get("Moderate");

moderate.add(item);

} else {

var expensive = itemsByCategories.get("Expensive");

expensive.add(item);

}

});

return itemsByCategories;

}

public static void printReport(Map<String, List<Item>> itemsByCategories) {

final DecimalFormat decimalFormatter = new DecimalFormat("0.00");

String output = CATEGORIES.stream().map(category -> {

var itemsByCategory = itemsByCategories.get(category);

StringBuilder message = new StringBuilder();

message.append("Category: ");

message.append(category);

message.append("\n");

message.append("Total Items: ");

message.append(itemsByCategory.size());

message.append("\n");

var discount = 0.0;

var totalByCategory = 0.0;

var totalDiscount = 0.0;

var totalAfterDiscount = 0.0;

if (itemsByCategory.size() > 0) {

if (category.equals("Cheap")) {

discount = 0.05;

} else if (category.equals("Moderate")) {

discount = 0.1;

} else if (category.equals("Expensive")) {

discount = 0.15;

}

totalByCategory = itemsByCategory.stream().map(Item::getPrice).collect(Collectors.summingDouble(n -> n));

totalDiscount = totalByCategory * discount;

totalAfterDiscount = totalByCategory - totalDiscount;

}

message.append("Total Discount: ");

message.append(decimalFormatter.format(totalDiscount));

message.append("\n");

message.append("Total After Discount: ");

message.append(decimalFormatter.format(totalAfterDiscount));

return message.toString();

})

.collect(Collectors.joining("\n\n"));

System.out.println(output);

}

}

class Item {

private String name;

private double price;

// constructor, getters, setters

public Item(String name, double price) {

this.name = name;

this.price = price;

}

public String getName() {

return this.name;

}

public double getPrice() {

return this.price;

}

}