如何用JAVA写超市管理系统？

超市管理系统一般包含以下模块：商品管理、库存管理、销售管理、用户管理、权限管理、报表统计等。

以下是一个简单的超市管理系统的JAVA代码框架：

//商品类
public class Product {
    private String name;  //商品名称
    private double price; //商品价格
    private int count;    //商品库存数量

    //构造函数
    public Product(String name, double price, int count) {
        this.name = name;
        this.price = price;
        this.count = count;
    }

    //getter和setter方法
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    public int getCount() {
        return count;
    }

    public void setCount(int count) {
        this.count = count;
    }
}

//库存管理类
public class Inventory {
    private List<Product> products;  //商品列表

    //构造函数
    public Inventory() {
        this.products = new ArrayList<Product>();
    }

    //添加商品
    public void addProduct(Product product) {
        products.add(product);
    }

    //根据名称查找商品
    public Product findProductByName(String name) {
        for (Product product : products) {
            if (product.getName().equals(name)) {
                return product;
            }
        }
        return null;
    }

    //更新商品库存数量
    public void updateProductCount(String name, int count) {
        Product product = findProductByName(name);
        if (product != null) {
            product.setCount(count);
        }
    }
}

//销售管理类
public class Sales {
    private List<Order> orders;  //订单列表

    //构造函数
    public Sales() {
        this.orders = new ArrayList<Order>();
    }

    //添加订单
    public void addOrder(Order order) {
        orders.add(order);
    }

    //计算总销售额
    public double getTotalSales() {
        double totalSales = 0;
        for (Order order : orders) {
            totalSales += order.getTotalPrice();
        }
        return totalSales;
    }
}

//订单类
public class Order {
    private List<OrderItem> items;  //订单项列表

    //构造函数
    public Order() {
        this.items = new ArrayList<OrderItem>();
    }

    //添加订单项
    public void addOrderItem(OrderItem item) {
        items.add(item);
    }

    //计算订单总价
    public double getTotalPrice() {
        double totalPrice = 0;
        for (OrderItem item : items) {
            totalPrice += item.getTotalPrice();
        }
        return totalPrice;
    }
}

//订单项类
public class OrderItem {
    private Product product;  //商品
    private int count;        //数量

    //构造函数
    public OrderItem(Product product, int count) {
        this.product = product;
        this.count = count;
    }

    //计算订单项总价
    public double getTotalPrice() {
        return product.getPrice() * count;
    }
}

//用户类
public class User {
    private String username;  //用户名
    private String password;  //密码
    private int role;         //角色

    //构造函数
    public User(String username, String password, int role) {
        this.username = username;
        this.password = password;
        this.role = role;
    }

    //getter和setter方法
    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public int getRole() {
        return role;
    }

    public void setRole(int role) {
        this.role = role;
    }
}

//权限管理类
public class Authorization {
    private Map<String, Integer> roles;  //角色列表

    //构造函数
    public Authorization() {
        this.roles = new HashMap<String, Integer>();
    }

    //添加角色
    public void addRole(String username, int role) {
        roles.put(username, role);
    }

    //根据用户名查找角色
    public int findRoleByUsername(String username) {
        if (roles.containsKey(username)) {
            return roles.get(username);
        }
        return -1;
    }
}

//主函数
public class Main {
    public static void main(String[] args) {
        //初始化商品列表
        Inventory inventory = new Inventory();
        Product product1 = new Product("可乐", 3.0, 100);
        Product product2 = new Product("薯片", 5.0, 50);
        inventory.addProduct(product1);
        inventory.addProduct(product2);

        //创建订单
        Order order = new Order();
        OrderItem item1 = new OrderItem(product1, 2);
        OrderItem item2 = new OrderItem(product2, 3);
        order.addOrderItem(item1);
        order.addOrderItem(item2);

        //添加订单到销售列表
        Sales sales = new Sales();
        sales.addOrder(order);

        //输出销售总额
        System.out.println("总销售额: " + sales.getTotalSales());
    }
}

以上代码只是一个简单的框架，实际开发中还需要考虑更多的细节问题。