Java如何做一个命令行点餐系统_菜单结构与价格计算逻辑

public class MenuItem {
    private String name;
    private double price;
    private String category;
<pre class="brush:php;toolbar:false;"><pre class="brush:php;toolbar:false;">public MenuItem(String name, double price, String category) {
    this.name = name;
    this.price = price;
    this.category = category;
}

// getter 方法
public String getName() { return name; }
public double getPrice() { return price; }
public String getCategory() { return category; }

@Override
public String toString() {
    return name + " - ¥" + String.format("%.2f", price);
}

import java.util.*;
<p>public class Menu {
private List<MenuItem> items;</p><pre class="brush:php;toolbar:false;"><pre class="brush:php;toolbar:false;">public Menu() {
    items = new ArrayList<>();
    loadDefaultMenu();
}

private void loadDefaultMenu() {
    items.add(new MenuItem("宫保鸡丁", 32.0, "主菜"));
    items.add(new MenuItem("红烧肉", 38.0, "主菜"));
    items.add(new MenuItem("可乐", 5.0, "饮料"));
    items.add(new MenuItem("奶茶", 12.0, "饮料"));
    items.add(new MenuItem("冰淇淋", 10.0, "甜点"));
}

public void display() {
    Map<String, List<MenuItem>> grouped = items.stream()
        .collect(Collectors.groupingBy(MenuItem::getCategory));

    for (Map.Entry<String, List<MenuItem>> entry : grouped.entrySet()) {
        System.out.println("\n【" + entry.getKey() + "】");
        List<MenuItem> list = entry.getValue();
        for (int i = 0; i < list.size(); i++) {
            System.out.println((i + 1) + ". " + list.get(i));
        }
    }
}

public MenuItem getItem(int index, String category) {
    List<MenuItem> filtered = items.stream()
        .filter(item -> item.getCategory().equals(category))
        .toList();
    if (index < 1 || index > filtered.size()) return null;
    return filtered.get(index - 1);
}

public List<String> getCategories() {
    return items.stream()
        .map(MenuItem::getCategory)
        .distinct()
        .toList();
}

public class OrderItem {
    private MenuItem item;
    private int quantity;
<pre class="brush:php;toolbar:false;"><pre class="brush:php;toolbar:false;">public OrderItem(MenuItem item, int quantity) {
    this.item = item;
    this.quantity = quantity;
}

public double getSubtotal() {
    return item.getPrice() * quantity;
}

public void addQuantity(int amount) {
    this.quantity += amount;
}

@Override
public String toString() {
    return item.getName() + " x" + quantity + " = ¥" + String.format("%.2f", getSubtotal());
}

// getter
public MenuItem getItem() { return item; }
public int getQuantity() { return quantity; }

import java.util.*;
<p>public class Order {
private List<OrderItem> items;</p><pre class="brush:php;toolbar:false;"><pre class="brush:php;toolbar:false;">public Order() {
    items = new ArrayList<>();
}

public void addItem(MenuItem menuItem, int quantity) {
    for (OrderItem orderItem : items) {
        if (orderItem.getItem().getName().equals(menuItem.getName())) {
            orderItem.addQuantity(quantity);
            return;
        }
    }
    items.add(new OrderItem(menuItem, quantity));
}

public double getTotal() {
    return items.stream()
        .mapToDouble(OrderItem::getSubtotal)
        .sum();
}

public void printOrder() {
    if (items.isEmpty()) {
        System.out.println("当前订单为空。");
        return;
    }
    System.out.println("\n--- 当前订单 ---");
    for (OrderItem item : items) {
        System.out.println(item);
    }
    System.out.println("总计：¥" + String.format("%.2f", getTotal()));
}

import java.util.Scanner;
<p>public class DiningSystem {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
Menu menu = new Menu();
Order order = new Order();</p><pre class="brush:php;toolbar:false;"><pre class="brush:php;toolbar:false;">    while (true) {
        System.out.println("\n=== 点餐系统 ===");
        System.out.println("1. 查看菜单");
        System.out.println("2. 添加菜品");
        System.out.println("3. 查看当前订单");
        System.out.println("4. 结账退出");
        System.out.print("请选择操作：");

        int choice = sc.nextInt();
        sc.nextLine(); // 消费换行

        switch (choice) {
            case 1:
                menu.display();
                break;
            case 2:
                addDish(sc, menu, order);
                break;
            case 3:
                order.printOrder();
                break;
            case 4:
                order.printOrder();
                System.out.println("感谢用餐！");
                sc.close();
                return;
            default:
                System.out.println("无效选择，请重试。");
        }
    }
}

private static void addDish(Scanner sc, Menu menu, Order order) {
    System.out.println("可选分类：");
    List<String> categories = menu.getCategories();
    for (int i = 0; i < categories.size(); i++) {
        System.out.println((i + 1) + ". " + categories.get(i));
    }
    System.out.print("选择分类编号：");
    int catIndex = sc.nextInt();
    if (catIndex < 1 || catIndex > categories.size()) {
        System.out.println("无效分类。");
        return;
    }
    String category = categories.get(catIndex - 1);

    System.out.println("该分类下的菜品：");
    List<MenuItem> items = new ArrayList<>(menu.items.stream()
        .filter(item -> item.getCategory().equals(category))
        .toList());
    for (int i = 0; i < items.size(); i++) {
        System.out.println((i + 1) + ". " + items.get(i));
    }
    System.out.print("选择菜品编号：");
    int itemIndex = sc.nextInt();
    MenuItem selected = menu.getItem(itemIndex, category);
    if (selected == null) {
        System.out.println("无效菜品编号。");
        return;
    }
    System.out.print("输入数量：");
    int qty = sc.nextInt();
    if (qty <= 0) {
        System.out.println("数量必须大于0。");
        return;
    }
    order.addItem(selected, qty);
    System.out.println("已添加：" + selected.getName() + " x" + qty);
}