src/chapter4/Example25.java

@@ -1,4 +0,0 @@
-package chapter4;
-
-public class Examaple25 {
-}

src/chapter4/demo45/Main.java

@@ -16,8 +16,7 @@ public class Main {
                 case 1: // 圆形
                     System.out.print("请输入圆形的半径：");
                     double radius = sc.nextDouble();
-                    Circle circle = new Circle(radius);
+                    Shape circle = new Circle(radius);
-//                    Shape circle = new Circle(radius);
                     ShapeCalculate.printArea(circle);
                     ShapeCalculate.printPerimeter(circle);
                     break;
@@ -25,8 +24,7 @@ public class Main {
                     System.out.print("请输入长方形的长和宽：");
                     double length = sc.nextDouble();
                     double width = sc.nextDouble();
-//                    Shape rectangle = new Rectangle(length, width);
+                    Shape rectangle = new Rectangle(length, width);
-                    Rectangle rectangle = new Rectangle(length, width);
                     ShapeCalculate.printArea(rectangle);
                     ShapeCalculate.printPerimeter(rectangle);
                     break;

src/chapter4/demo45/ShapeCalculate.java

@@ -13,33 +13,12 @@ public final class ShapeCalculate {
 
     // 打印图形面积
     public static void printArea(Shape shape) {
-        if (shape instanceof Rectangle) {
+        System.out.println("面积："+shape.getArea());
-            System.out.println("正方形面积："+shape.getArea());
-        } else if (shape instanceof Circle) {
-            System.out.println("圆形面积："+shape.getArea());
-        } else {
-            System.out.println("未知图形面积：" + shape.getArea());
-        }
     }
 
     // 打印图形周长
-//    public static void printPerimeter(Shape shape) {
+    public static void printPerimeter(Shape shape) {
-//        if (shape instanceof Rectangle) {
+        System.out.println("周长："+shape.getPerimeter());
-//            System.out.print("长方形");
-//        } else if (shape instanceof Circle) {
-//            System.out.print("圆形");
-//        } else {
-//            System.out.print("未知图形");
-//        }
-//        System.out.println("周长："+shape.getPerimeter());
-//    }
-
-    public static void printPerimeter(Circle circle) {
-        System.out.println("圆形周长："+circle.getPerimeter());
-    }
-
-    public static void printPerimeter(Rectangle rectangle) {
-        System.out.println("长方形周长："+rectangle.getPerimeter());
     }
 
     // 打印计算器菜单

src/chapter4/demo49/Main.java

@@ -1,90 +0,0 @@
-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

@@ -1,73 +0,0 @@
-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

@@ -1,54 +0,0 @@
-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();
-        }
-    }
-}

src/chapter4/example14/Example14.java

@@ -1,2 +0,0 @@
-package chapter4.example14;public class Example14 {
-}

src/chapter4/object/Test.java

@@ -1,19 +0,0 @@
-package chapter4.object;
-
-class Student {
-    private String name;
-    private int age;
-
-    public Student(String name, int age) {
-        this.name = name;
-        this.age = age;
-    }
-
-    public String toString() {
-        return "Student {name=" + name + ", age=" + age + "}";
-    }
-}
-
-public class Test {
-
-}