用户管理高级版

src/chapter4/demo49/Main.java

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+package chapter4.demo49;
+
+import java.util.Scanner;
+
+public class Main {
+    // 处理用户的输入
+    private static Scanner scanner = new Scanner(System.in);
+    // 用户管理器
+    private static UserManager userManager = UserManager.getInstance();
+    // 当前登录用户
+    private static AbstractUser currentUser = null;
+
+    public static void main(String[] args) {
+        while (true) {
+            printMainMenu();
+
+            try {
+                int choice = scanner.nextInt();
+                switch (choice) {
+                    case 1:
+                        login();
+                        break;
+                    case 2:
+                        register();
+                        break;
+                    case 3:
+                        if (currentUser instanceof AdminUser) {
+                            userManager.showAllUsers();
+                        } else {
+                            System.out.println("权限不足！");
+                        }
+                        break;
+                    case 4:
+                        if (currentUser instanceof AdminUser) {
+                            System.out.print("请输入要删除的用户名：");
+                            String username = scanner.next();
+                            userManager.removeUser(username);
+                            System.out.println("删除用户成功！");
+                        } else {
+                            System.out.println("权限不足！");
+                        }
+                        break;
+                    case 0:
+                        System.out.println("谢谢使用，再见！");
+                        System.exit(0);
+                    default:
+                        System.out.println("无效的选择！");
+                }
+            } catch (Exception e) {
+                System.out.println("发生错误：" + e.getMessage());
+                scanner.nextLine(); // 清除输入缓冲
+            }
+        }
+    }
+
+    private static void printMainMenu() {
+        System.out.println("\n=====用户管理系统=====");
+        System.out.println("1. 用户登录");
+        System.out.println("2. 用户注册");
+        System.out.println("3. 查看用户列表（需管理员权限）");
+        System.out.println("4. 删除用户（需管理员权限）");
+        System.out.println("0. 退出系统");
+        System.out.println("请选择功能：");
+    }
+
+    private static void login() throws UserException {
+        System.out.print("请输入用户名：");
+        String username = scanner.next();
+        System.out.print("请输入密码：");
+        String password = scanner.next();
+
+        currentUser = userManager.login(username, password);
+        System.out.println("登录成功！欢迎 " + currentUser.getUsername());
+
+        if (currentUser instanceof AdminUser) {
+            System.out.println("您以管理员身份登录");
+        }
+    }
+
+    private static void register() throws UserException {
+        System.out.print("请输入用户名：");
+        String username = scanner.next();
+        System.out.print("请输入密码：");
+        String password = scanner.next();
+
+        NormalUser newUser = new NormalUser(username, password);
+        userManager.addUser(newUser);
+        System.out.println("注册成功！");
+    }
+}

src/chapter4/demo49/User.java

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+package chapter4.demo49;
+
+// 自定义异常类
+class UserException extends Exception {
+    public UserException(String message) {
+        super(message);
+    }
+}
+
+// 用户操作接口
+interface UserOperation {
+    void changePassword(String newPassword) throws UserException;
+    void showInfo();
+}
+
+// 抽象用户类
+abstract class AbstractUser implements UserOperation {
+    protected String username;      // 用户名
+    protected String password;      // 密码
+    protected String userType;      // 用户类型
+
+    // 构造方法
+    public AbstractUser(String username, String password) {
+        this.username = username;
+        this.password = password;
+    }
+
+    public String getUsername() {
+        return username;
+    }
+
+    // 检查密码是否正确
+    public boolean checkPassword(String password) {
+        return this.password.equals(password);
+    }
+
+    @Override
+    public void showInfo() {
+        System.out.println("用户名：" + username + "，用户类型：" + userType);
+    }
+}
+
+// 普通用户类
+class NormalUser extends AbstractUser {
+    public NormalUser(String username, String password) {
+        super(username, password);
+        this.userType = "普通用户";
+    }
+
+    @Override
+    public void changePassword(String newPassword) throws UserException {
+        if (newPassword.length() < 6) {
+            throw new UserException("密码长度不能小于6位");
+        }
+        this.password = newPassword;
+    }
+}
+
+// 管理员类
+class AdminUser extends AbstractUser {
+    public AdminUser(String username, String password) {
+        super(username, password);
+        this.userType = "管理员";
+    }
+
+    @Override
+    public void changePassword(String newPassword) throws UserException {
+        if (newPassword.length() < 8) {
+            throw new UserException("管理员密码长度不能小于8位");
+        }
+        this.password = newPassword;
+    }
+}

src/chapter4/demo49/UserManager.java

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+package chapter4.demo49;
+
+import java.util.HashMap;
+import java.util.Map;
+
+class UserManager {
+    // 保证单例模式
+    private static UserManager instance;
+    // 存储所有用户
+    private Map<String, AbstractUser> users;
+
+    private UserManager() {
+        users = new HashMap<>();
+        // 初始化一个管理员账号
+        users.put("admin", new AdminUser("admin", "admin123"));
+    }
+
+    // 单例模式
+    public static UserManager getInstance() {
+        if (instance == null) {
+            instance = new UserManager();
+        }
+        return instance;
+    }
+
+    public void addUser(AbstractUser user) throws UserException {
+        if (users.containsKey(user.getUsername())) {
+            throw new UserException("用户名已存在！");
+        }
+        users.put(user.getUsername(), user);
+    }
+
+    public AbstractUser login(String username, String password) throws UserException {
+        AbstractUser user = users.get(username);
+        if (user == null) {
+            throw new UserException("用户不存在！");
+        }
+        if (!user.checkPassword(password)) {
+            throw new UserException("用户名或密码错误！");
+        }
+        return user;
+    }
+
+    public void removeUser(String username) {
+        users.remove(username);
+    }
+
+    public void showAllUsers() {
+        System.out.println("当前系统用户列表：");
+        for (AbstractUser user : users.values()) {
+            user.showInfo();
+        }
+    }
+}