java 保存

Java/TodoListApp/EmptyDescriptionException.java

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+package TodoListApp;
+public class EmptyDescriptionException extends Exception {
+    public EmptyDescriptionException(String message){
+        super(message);
+    }
+}

Java/TodoListApp/InvalidIdException.java

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+package TodoListApp;
+public class InvalidIdException extends Exception {
+    public InvalidIdException(String message){
+        super(message);
+    }
+}

Java/TodoListApp/TodoItem.java

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+package TodoListApp;
+// 待办事项类
+class TodoItem {
+    private int id;
+    private String description;
+    private boolean isCompleted;
+
+    public TodoItem(int id, String description) {
+        this.id = id;
+        this.description = description;
+        this.isCompleted = false;
+    }
+
+    // Getter方法
+    public int getId() {
+        return id;
+    }
+
+    public boolean isCompleted() {
+        return isCompleted;
+    }
+
+    public void setCompleted(boolean completed) {
+        isCompleted = completed;
+    }
+
+    public String getDescription() {
+        return description;
+    }
+
+    // 显示待办事项信息
+    @Override
+    public String toString() {
+        String status = isCompleted? "[已完成]" : "[未完成]";
+        return String.format("[%d] %s %s", id,status, description);
+    }
+}

Java/TodoListApp/TodoListApp.java

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+package TodoListApp;
+import java.util.Scanner;
+
+// 主类
+public class TodoListApp {
+    private static final String ADD_TODO = "1";
+    private static final String LIST_TODOS = "2";
+    private static final String REMOVE_TODO = "3";
+    private static final String MARK_AS_COMPLETED = "4";
+    private static final String SAVE_TODOS = "5";
+    private static final String EXIT = "6";
+
+    private static final TodoListManager manager = new TodoListManager();
+    private static final Scanner scanner = new Scanner(System.in);
+
+    public static void main(String[] args) {
+        boolean exit = false;
+        while (!exit) {
+            printMenu();
+            String choice = scanner.nextLine();
+            switch (choice) {
+                case ADD_TODO:
+                    addTodoUI();
+                    break;
+                case LIST_TODOS:
+                    manager.listTodos();
+                    break;
+                case REMOVE_TODO:
+                    removeTodoUI();
+                    break;
+                case MARK_AS_COMPLETED:
+                    markAsCompletedUI();
+                    break;
+                case SAVE_TODOS:
+                    manager.saveToFile("todos.dat");
+                    break;
+                case EXIT:
+                    exit = true;
+                    System.out.println("退出程序。");
+                    break;
+                default:
+                    System.out.println("无效的选择，请重新输入。");
+            }
+        }
+        scanner.close();
+    }
+
+    // 打印菜单
+    private static void printMenu() {
+        System.out.println("\n===== 简易待办事项管理器 =====");
+        System.out.println("1. 添加待办事项");
+        System.out.println("2. 查看所有待办事项");
+        System.out.println("3. 删除待办事项");
+        System.out.println("4. 标记待办为已完成");
+        System.out.println("5. 保存待办事项（字节流）");
+        System.out.println("6. 退出");
+        System.out.print("请选择操作（1-6）：");
+    }
+
+    // 添加待办事项的用户界面
+    private static void addTodoUI() {
+        String description = getNonEmptyInput("请输入待办事项描述：");
+        try {
+            manager.addTodo(description);
+        } catch (EmptyDescriptionException e) {
+            System.out.println("自定义异常：" + e.getMessage());
+        }
+    }
+
+    // 删除待办事项的用户界面
+    private static void removeTodoUI() {
+        System.out.print("请输入要删除的待办事项编号：");
+        String input = scanner.nextLine().trim();
+        try {
+            int id = Integer.parseInt(input);
+            manager.removeTodo(id);
+        } catch (NumberFormatException e) {
+            try {
+                throw new InvalidIdException("请输入有效的ID编号。");
+            } catch (InvalidIdException ex) {
+                System.out.println("自定义异常：" + ex.getMessage());
+                ;
+            }
+        } catch (TodoNotFoundException e) {
+            System.out.println("自定义异常：" + e.getMessage());
+        }
+    }
+
+    //用于对用户的输入进行提示和预处理的能用方法
+    private static String getNonEmptyInput(String prompt) {
+        System.out.println(prompt);
+        String input = scanner.nextLine().trim();
+        while (input.isEmpty()) {
+            System.out.println("输入不能为空，请重新输入。");
+            System.out.println(prompt);
+            input = scanner.nextLine().trim();
+        }
+        return input;
+    }
+
+    private static void markAsCompletedUI() {
+        String input = getNonEmptyInput("请输入要标记为已完成的待办事项编号：");
+        try {
+            int id = Integer.parseInt(input);
+            manager.markAsCompleted(id);
+        } catch (NumberFormatException e) {
+            System.out.println("请输入有效的数字编号。");
+        }
+    }
+}

Java/TodoListApp/TodoListManager.java

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+package TodoListApp;
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.time.LocalDateTime;
+import java.time.format.DateTimeFormatter;
+
+// 待办事项管理类
+class TodoListManager {
+    private final List<TodoItem> todoList;
+    private int nextId;
+
+    public TodoListManager() {
+        todoList = new ArrayList<>();
+        nextId = 1; // 起始编号
+    }
+
+    // 添加待办事项
+    public void addTodo(String description) throws EmptyDescriptionException{ //同时声明可能抛出的异常类型
+        if(description == null || description.trim().isEmpty()){
+            EmptyDescriptionException e = new EmptyDescriptionException("待办事项的描述不能为空。");
+            throw e;
+        }
+        try {
+            string sql = "insert into todos (description) values('"+description+"')"
+            system.out.println(sql);
+            Statement stmt = conn.createStatement();
+            stmt.executeUpdate(sql)
+        }
+        TodoItem item = new TodoItem(nextId++, description);
+        todoList.add(item);
+        System.out.println("待办事项已添加： " + item);
+    }o
+
+    // 列出所有待办事项
+    public void listTodos() {
+        if (todoList.isEmpty()) {
+            System.out.println("当前没有待办事项。");
+            return;
+        }
+        System.out.println("\n===== 待办事项列表 =====");
+        for (TodoItem item : todoList) {
+            System.out.println(item);
+        }
+    }
+
+    // 删除指定编号的待办事项
+    public void removeTodo(int id) throws TodoNotFoundException{
+        boolean removed = false;
+        for (TodoItem item : todoList) {
+            if (item.getId() == id) {
+                todoList.remove(item);
+                System.out.println("已删除待办事项： " + item);
+                removed = true;
+                break;
+            }
+        }
+        if (!removed) {
+            throw new TodoNotFoundException("未找到编号为 " + id + " 的待办事项。");
+            //System.out.println("未找到编号为 " + id + " 的待办事项。");
+        }
+    }
+
+    public void markAsCompleted(int id) {
+        TodoItem item = null;
+        for (TodoItem todo : todoList) {
+            if (todo.getId() == id) {
+                item = todo;
+                break;
+            }
+
+        }
+        if (item != null) {
+            if (!item.isCompleted()) {
+                item.setCompleted(true);
+                System.out.println("待办事项已标记为完成： " + item);
+            } else {
+                System.out.println("待办事项已完成，无需重复标记。");
+            }
+        }
+        else {
+            System.out.println("未找到编号为：" + id + " 的待办事项。");
+        }
+    }
+
+    public void saveToFile(String filename){
+
+        try {
+            File file = new File(filename);
+            FileOutputStream fos = new FileOutputStream(file);
+
+            for (TodoItem item : todoList) {
+                String line = item.getId() + ":" + item.getDescription() + "\n";
+                fos.write(line.getBytes());
+            }
+            System.out.println("待办事项已经保存到文件：" + filename);
+
+            fos.close();
+        }
+        catch (IOException e){
+            System.out.println("待办事项保存失败：" + e.getMessage());
+        }
+    }
+
+    private void backupToFile(String backupFilename) {
+        LocalDateTime now = LocalDateTime.now();
+        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd_HH-mm-ss");
+        String timestamp = now.format(formatter);
+        String fullBackupFilename = backupFilename + "_" + timestamp + ".bak";
+
+        try (FileOutputStream fos = new FileOutputStream(new File(fullBackupFilename))) {
+            for (TodoItem item : todoList) {
+                String line = item.getId() + ":" + item.getDescription() + ":" + (item.isCompleted() ? "完成" : "未完成") + "\n";
+                fos.write(line.getBytes());
+            }
+            System.out.println("待办事项已备份到文件：" + fullBackupFilename);
+        } catch (IOException e) {
+            System.out.println("待办事项备份失败：" + e.getMessage());
+        }
+    }
+}

Java/TodoListApp/TodoNotFoundException.java

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+package TodoListApp;
+public class TodoNotFoundException extends Exception {
+    public TodoNotFoundException(String message){
+        super(message);
+    }
+}

Java/TodoListApp/todos.dat

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+1:123123