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综合项目

本课是Java教程的最终项目，综合运用所有知识点。

项目概述

实现一个命令行待办清单（Todo List）应用，支持：

数据模型

JAVA 
import java.io.Serializable;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

public class Todo implements Serializable {
    private static final long serialVersionUID = 1L;
    
    public enum Priority { LOW, MEDIUM, HIGH }
    public enum Status { PENDING, COMPLETED }
    
    private int id;
    private String title;
    private String description;
    private Priority priority;
    private Status status;
    private LocalDateTime createdAt;
    private LocalDateTime completedAt;
    
    public Todo(int id, String title, String description, Priority priority) {
        this.id = id;
        this.title = title;
        this.description = description;
        this.priority = priority;
        this.status = Status.PENDING;
        this.createdAt = LocalDateTime.now();
    }
    
    // getter/setter
    public int getId() { return id; }
    public String getTitle() { return title; }
    public String getDescription() { return description; }
    public Priority getPriority() { return priority; }
    public Status getStatus() { return status; }
    public LocalDateTime getCreatedAt() { return createdAt; }
    public LocalDateTime getCompletedAt() { return completedAt; }
    
    public void setStatus(Status status) {
        this.status = status;
        if (status == Status.COMPLETED) {
            this.completedAt = LocalDateTime.now();
        }
    }
    
    public boolean isCompleted() {
        return status == Status.COMPLETED;
    }
    
    @Override
    public String toString() {
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm");
        String statusIcon = isCompleted() ? "✅" : "⬜";
        String priorityIcon;
        switch (priority) {
            case HIGH: priorityIcon = "🔴"; break;
            case MEDIUM: priorityIcon = "🟡"; break;
            default: priorityIcon = "🟢"; break;
        }
        return String.format("%s %s [%d] %s (%s)", 
            statusIcon, priorityIcon, id, title, createdAt.format(formatter));
    }
}

管理类

JAVA 
import java.io.*;
import java.util.*;
import java.util.stream.Collectors;

public class TodoManager {
    private List<Todo> todos;
    private int nextId;
    private static final String FILE_NAME = "todos.dat";
    
    public TodoManager() {
        this.todos = new ArrayList<>();
        this.nextId = 1;
        loadFromFile();
    }
    
    // 添加待办
    public Todo addTodo(String title, String description, Todo.Priority priority) {
        Todo todo = new Todo(nextId++, title, description, priority);
        todos.add(todo);
        saveToFile();
        return todo;
    }
    
    // 完成待办
    public boolean completeTodo(int id) {
        Todo todo = findById(id);
        if (todo != null && !todo.isCompleted()) {
            todo.setStatus(Todo.Status.COMPLETED);
            saveToFile();
            return true;
        }
        return false;
    }
    
    // 删除待办
    public boolean deleteTodo(int id) {
        Todo todo = findById(id);
        if (todo != null) {
            todos.remove(todo);
            saveToFile();
            return true;
        }
        return false;
    }
    
    // 查找待办
    public Todo findById(int id) {
        return todos.stream()
            .filter(t -> t.getId() == id)
            .findFirst()
            .orElse(null);
    }
    
    // 获取所有待办
    public List<Todo> getAllTodos() {
        return new ArrayList<>(todos);
    }
    
    // 获取待处理的待办
    public List<Todo> getPendingTodos() {
        return todos.stream()
            .filter(t -> !t.isCompleted())
            .collect(Collectors.toList());
    }
    
    // 获取已完成的待办
    public List<Todo> getCompletedTodos() {
        return todos.stream()
            .filter(Todo::isCompleted)
            .collect(Collectors.toList());
    }
    
    // 按优先级排序
    public List<Todo> sortByPriority() {
        return todos.stream()
            .sorted((a, b) -> {
                int cmp = b.getPriority().compareTo(a.getPriority());
                return cmp != 0 ? cmp : a.getId() - b.getId();
            })
            .collect(Collectors.toList());
    }
    
    // 按创建时间排序
    public List<Todo> sortByDate() {
        return todos.stream()
            .sorted(Comparator.comparing(Todo::getCreatedAt))
            .collect(Collectors.toList());
    }
    
    // 统计
    public int getTotal() { return todos.size(); }
    public int getPendingCount() { return (int) todos.stream().filter(t -> !t.isCompleted()).count(); }
    public int getCompletedCount() { return (int) todos.stream().filter(Todo::isCompleted).count(); }
    
    // 保存到文件
    private void saveToFile() {
        try (ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(FILE_NAME))) {
            oos.writeObject(todos);
            oos.writeInt(nextId);
        } catch (IOException e) {
            System.out.println("保存失败：" + e.getMessage());
        }
    }
    
    // 从文件加载
    @SuppressWarnings("unchecked")
    private void loadFromFile() {
        File file = new File(FILE_NAME);
        if (!file.exists()) return;
        
        try (ObjectInputStream ois = new ObjectInputStream(new FileInputStream(FILE_NAME))) {
            todos = (List<Todo>) ois.readObject();
            nextId = ois.readInt();
        } catch (IOException | ClassNotFoundException e) {
            System.out.println("加载失败：" + e.getMessage());
        }
    }
}

主程序

JAVA 
import java.util.List;
import java.util.Scanner;

public class TodoApp {
    private static TodoManager manager = new TodoManager();
    private static Scanner scanner = new Scanner(System.in);
    
    public static void main(String[] args) {
        System.out.println("=== 待办清单 ===");
        
        int choice;
        do {
            showMenu();
            choice = getIntInput("请选择：");
            
            switch (choice) {
                case 1: addTodo(); break;
                case 2: listTodos(); break;
                case 3: completeTodo(); break;
                case 4: deleteTodo(); break;
                case 5: showStatistics(); break;
                case 6: listByPriority(); break;
                case 0: System.out.println("再见！"); break;
                default: System.out.println("无效选择");
            }
        } while (choice != 0);
        
        scanner.close();
    }
    
    private static void showMenu() {
        System.out.println("\n--- 菜单 ---");
        System.out.println("1. 添加待办");
        System.out.println("2. 查看所有待办");
        System.out.println("3. 标记完成");
        System.out.println("4. 删除待办");
        System.out.println("5. 统计信息");
        System.out.println("6. 按优先级排序");
        System.out.println("0. 退出");
    }
    
    private static void addTodo() {
        System.out.print("标题：");
        String title = scanner.nextLine().trim();
        if (title.isEmpty()) {
            System.out.println("标题不能为空");
            return;
        }
        
        System.out.print("描述：");
        String desc = scanner.nextLine().trim();
        
        System.out.println("优先级：1-低 2-中 3-高");
        int p = getIntInput("选择：");
        Todo.Priority priority;
        switch (p) {
            case 1: priority = Todo.Priority.LOW; break;
            case 3: priority = Todo.Priority.HIGH; break;
            default: priority = Todo.Priority.MEDIUM;
        }
        
        Todo todo = manager.addTodo(title, desc, priority);
        System.out.println("添加成功：" + todo);
    }
    
    private static void listTodos() {
        List<Todo> todos = manager.getAllTodos();
        if (todos.isEmpty()) {
            System.out.println("暂无待办事项");
            return;
        }
        
        System.out.println("\n--- 待办列表 ---");
        for (Todo todo : todos) {
            System.out.println(todo);
        }
        System.out.printf("共 %d 项（待处理 %d，已完成 %d）%n", 
            manager.getTotal(), manager.getPendingCount(), manager.getCompletedCount());
    }
    
    private static void completeTodo() {
        listTodos();
        int id = getIntInput("输入要完成的ID：");
        if (manager.completeTodo(id)) {
            System.out.println("已标记完成");
        } else {
            System.out.println("ID无效或已完成");
        }
    }
    
    private static void deleteTodo() {
        listTodos();
        int id = getIntInput("输入要删除的ID：");
        if (manager.deleteTodo(id)) {
            System.out.println("已删除");
        } else {
            System.out.println("ID无效");
        }
    }
    
    private static void showStatistics() {
        System.out.println("\n=== 统计信息 ===");
        System.out.println("总计：" + manager.getTotal());
        System.out.println("待处理：" + manager.getPendingCount());
        System.out.println("已完成：" + manager.getCompletedCount());
        double rate = manager.getTotal() > 0 ? 
            (double) manager.getCompletedCount() / manager.getTotal() * 100 : 0;
        System.out.printf("完成率：%.1f%%%n", rate);
    }
    
    private static void listByPriority() {
        List<Todo> todos = manager.sortByPriority();
        System.out.println("\n--- 按优先级排序 ---");
        for (Todo todo : todos) {
            System.out.println(todo);
        }
    }
    
    private static int getIntInput(String prompt) {
        System.out.print(prompt);
        while (!scanner.hasNextInt()) {
            System.out.print("请输入数字：");
            scanner.next();
        }
        int value = scanner.nextInt();
        scanner.nextLine();  // 消耗换行符
        return value;
    }
}

运行示例

TEXT 
=== 待办清单 ===

--- 菜单 ---
1. 添加待办
2. 查看所有待办
3. 标记完成
4. 删除待办
5. 统计信息
6. 按优先级排序
0. 退出
请选择：1
标题：学习Java
描述：完成Java教程第32课
优先级：1-低 2-中 3-高
选择：3
添加成功：⬜ 🔴 [1] 学习Java (2026-06-24 14:30)

请选择：2

--- 待办列表 ---
⬜ 🔴 [1] 学习Java (2026-06-24 14:30)
共 1 项（待处理 1，已完成 0）

知识点总结

知识点 应用
类与对象 Todo、TodoManager类设计
封装 属性私有，getter/setter
枚举 Priority、Status枚举
集合 List存储待办，Stream操作
异常处理 文件IO异常处理
文件IO 序列化保存/加载数据
日期时间 LocalDateTime记录时间
Lambda Stream排序、过滤
泛型 List类型安全

扩展功能

1. 按日期筛选

JAVA 
public List<Todo> getTodayTodos() {
    LocalDate today = LocalDate.now();
    return todos.stream()
        .filter(t -> t.getCreatedAt().toLocalDate().equals(today))
        .collect(Collectors.toList());
}

2. 搜索功能

JAVA 
public List<Todo> search(String keyword) {
    String lower = keyword.toLowerCase();
    return todos.stream()
        .filter(t -> t.getTitle().toLowerCase().contains(lower) ||
                     t.getDescription().toLowerCase().contains(lower))
        .collect(Collectors.toList());
}

3. 导出为文本

JAVA 
public void exportToText(String filename) throws IOException {
    try (PrintWriter writer = new PrintWriter(new FileWriter(filename))) {
        writer.println("=== 待办清单导出 ===");
        writer.println("导出时间：" + LocalDateTime.now());
        writer.println();
        
        for (Todo todo : todos) {
            writer.println(todo);
            if (!todo.getDescription().isEmpty()) {
                writer.println("  " + todo.getDescription());
            }
            writer.println();
        }
    }
}

❓ 常见问题

Q 如何扩展为GUI应用？
A 可以用JavaFX或Swing实现图形界面。
Q 如何支持多用户？
A 每个用户一个数据文件，或使用数据库存储。
Q 如何添加提醒功能？
A 使用定时器（Timer/ScheduledExecutorService）检查到期任务。

📖 小节

📝 作业

  1. 扩展功能： 添加搜索和按日期筛选功能
  2. 数据导出： 支持导出为CSV格式
  3. GUI版本： 用JavaFX实现图形界面版本

🎉 恭喜完成Java教程！

通过32节课的学习，你已经掌握了：

接下来可以继续学习：

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