ADD file via upload

src/Login.java

@@ -0,0 +1,133 @@
+import java.io.*;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Scanner;
+
+public class Login {
+	private static final String USER_FILE = "users.txt";
+    private static List<User> users = new ArrayList<>();
+    public void Main() {    	
+    	load();
+        Scanner scanner = new Scanner(System.in);        
+        while (true) {
+            System.out.println("\n---------登录系统---------");
+            System.out.println("请输入用户名和密码（用空格隔开）: ");
+            String input = scanner.nextLine().trim(); 
+            if (input.equalsIgnoreCase("q")) {
+                System.out.println("\n已退出！");
+                break;
+            } 
+            String[] NandP = input.split(" "); 
+            if (NandP.length != 2) {
+                System.out.println("请输入正确的用户名和密码！");
+                continue;
+            }
+            String username = NandP[0];
+            String password = NandP[1];
+            User user = Prove(username, password);
+            if (user != null) {
+                Success(user, scanner);
+            } else {
+                System.out.println("请输入正确的用户名和密码！");
+            }
+        }
+        scanner.close();
+    }
+      
+    private static void load() {
+        users.clear();
+        try (BufferedReader reader = new BufferedReader(new FileReader(USER_FILE))) {
+            String line;
+            while ((line = reader.readLine()) != null) {
+                line = line.trim();
+                if (!line.isEmpty()) {
+                    String[] parts = line.split(" ");
+                    if (parts.length == 3) {
+                        users.add(new User(parts[0], parts[1], parts[2]));
+                    }
+                }
+            }
+            reader.close();
+            System.out.println("Loading...");
+        } catch (IOException e) {
+            System.out.println("出错！" + e.getMessage());
+        }
+    }
+    
+    private static User Prove(String username, String password) {
+        for (User user : users) {
+            if (user.getUsername().equals(username) && user.getPassword().equals(password)) {
+                return user;
+            }
+        }
+        return null;
+    }
+    
+    private static void Success(User user, Scanner scanner) {
+    	String role = getRole(user.getRole());
+        System.out.println("\n登录成功！\n" + user.getUsername() + " [" + role + "]");
+        QuestionManager questionManager = new QuestionManager(user.getUsername(), user.getRole());
+        while (true) {
+            System.out.println("\n输入 -1 退出登录，输入 q 退出程序，输入\"切换为XX\"切换难度（XX为小学、初中、高中）");
+            System.out.println("准备生成[" + questionManager.getCurrentRoleChinese() + "]数学题目，请输入生成题目数量（10~30）：");
+            String input = scanner.nextLine().trim();
+            if (input.equals("-1")) {
+                System.out.println("返回登录界面...");
+                break;
+            } else if (input.equalsIgnoreCase("q")) {
+                System.out.println("\n已退出！");
+                System.exit(0);
+            } else if (input.startsWith("切换为")) {
+                Switch(questionManager, input);
+            } else {
+                try {
+                    int count = Integer.parseInt(input);
+                    if (count >= 10 && count <= 30) {
+                        questionManager.generateQuestions(count);
+                    } else if (count == -1) {
+                        System.out.println("返回登录界面...");
+                        break;
+                    } else {
+                        System.out.println("题目数量应在10~30之间!");
+                    }
+                } catch (NumberFormatException e) {
+                    System.out.println("请输入有效的数字（10~30）或指定命令!");
+                }
+            }
+        }
+    }
+    
+    private static void Switch(QuestionManager questionManager, String input) {
+    	String newRole = input.substring(3).trim();
+        switch (newRole) {
+            case "小学":
+                questionManager.setRole("primary");
+                System.out.println("已切换为小学难度");
+                break;
+            case "初中":
+                questionManager.setRole("junior");
+                System.out.println("已切换为初中难度");
+                break;
+            case "高中":
+                questionManager.setRole("senior");
+                System.out.println("已切换为高中难度");
+                break;
+            default:
+                System.out.println("请输入小学、初中和高中三个选项中的一个");
+        }
+    }
+    
+    private static String getRole(String role) {
+        switch (role) {
+            case "primary":
+                return "小学";
+            case "junior":
+                return "初中";
+            case "senior":
+                return "高中";
+            default:
+                return "未知";
+        }
+    }
+    
+}