Java集合框架入门：任务清单管理实战

public class Task {
    private String title;
    private boolean completed;
    private long createTime;
public Task(String title) {
    this.title = title;
    this.completed = false;
    this.createTime = System.currentTimeMillis();
}

// Getter 和 Setter 方法
public String getTitle() { return title; }
public boolean isCompleted() { return completed; }
public void setCompleted(boolean completed) { this.completed = completed; }
public long getCreateTime() { return createTime; }

@Override
public String toString() {
    return "[" + (completed ? "✓" : "○") + "] " + title;
}
}

import java.util.ArrayList;
import java.util.List;
public class TodoManager {
private List tasks = new ArrayList<>();
public void addTask(String title) {
    tasks.add(new Task(title));
}

public void removeTask(int index) {
    if (index >= 0 && index < tasks.size()) {
        tasks.remove(index);
    } else {
        System.out.println("无效的序号！");
    }
}

public void listTasks() {
    if (tasks.isEmpty()) {
        System.out.println("暂无任务。");
        return;
    }
    for (int i = 0; i < tasks.size(); i++) {
        System.out.println((i + 1) + ". " + tasks.get(i));
    }
}

public void markCompleted(int index) {
    if (index >= 0 && index < tasks.size()) {
        tasks.get(index).setCompleted(true);
    } else {
        System.out.println("无效的序号！");
    }
}
}

import java.util.HashSet;
import java.util.Set;
public class Task {
// ... 原有字段
private Set tags = new HashSet<>();
public void addTag(String tag) {
    tags.add(tag.toLowerCase());
}

public Set getTags() {
    return new HashSet<>(tags); // 返回副本，防止外部修改
}
}

import java.util.HashMap;
import java.util.Map;
public void printSummary() {
Map summary = new HashMap<>();
summary.put(true, 0);
summary.put(false, 0);
for (Task task : tasks) {
    boolean status = task.isCompleted();
    summary.put(status, summary.get(status) + 1);
}

System.out.println("总计：" + tasks.size() + " 个任务");
System.out.println("未完成：" + summary.get(false));
System.out.println("已完成：" + summary.get(true));
}

import java.util.Scanner;
public static void main(String[] args) {
TodoManager manager = new TodoManager();
Scanner sc = new Scanner(System.in);
System.out.println("欢迎使用任务清单系统！");
while (true) {
    System.out.println("\n1. 添加任务  2. 查看任务  3. 完成任务  4. 删除任务  5. 统计  6. 退出");
    System.out.print("请选择操作：");
    int choice = sc.nextInt();
    sc.nextLine(); // 消费换行符

    switch (choice) {
        case 1:
            System.out.print("输入任务内容：");
            String title = sc.nextLine();
            manager.addTask(title);
            break;
        case 2:
            manager.listTasks();
            break;
        case 3:
            System.out.print("输入要完成的任务序号：");
            int idx = sc.nextInt() - 1;
            manager.markCompleted(idx);
            break;
        case 4:
            System.out.print("输入要删除的任务序号：");
            int delIdx = sc.nextInt() - 1;
            manager.removeTask(delIdx);
            break;
        case 5:
            manager.printSummary();
            break;
        case 6:
            System.out.println("再见！");
            sc.close();
            return;
        default:
            System.out.println("无效选择，请重试。");
    }
}
}