Java里如何开发简易论坛帖子分类功能_帖子分类项目实战解析

public class Category {
    private int id;
    private String name;
<pre class='brush:java;toolbar:false;'>public Category(int id, String name) {
    this.id = id;
    this.name = name;
}

// getter 和 setter 省略

public class Post {
    private int id;
    private String title;
    private String content;
    private int categoryId;
<pre class='brush:java;toolbar:false;'>public Post(int id, String title, String content, int categoryId) {
    this.id = id;
    this.title = title;
    this.content = content;
    this.categoryId = categoryId;
}

// getter 和 setter 省略

import java.util.*;
<p>public class CategoryService {
private Map<Integer, Category> categoryMap = new HashMap<>();
private List<Post> postList = new ArrayList<>();
private int nextId = 1;</p><pre class='brush:java;toolbar:false;'>public void addCategory(String name) {
    if (name == null || name.trim().isEmpty()) {
        System.out.println("分类名不能为空");
        return;
    }
    for (Category c : categoryMap.values()) {
        if (c.getName().equals(name)) {
            System.out.println("分类已存在：" + name);
            return;
        }
    }
    categoryMap.put(nextId, new Category(nextId, name));
    System.out.println("分类添加成功：" + name + " (ID:" + nextId + ")");
    nextId++;
}

public void listCategories() {
    if (categoryMap.isEmpty()) {
        System.out.println("暂无分类");
        return;
    }
    System.out.println("\n=== 分类列表 ===");
    for (Category c : categoryMap.values()) {
        int postCount = (int) postList.stream()
            .filter(p -> p.getCategoryId() == c.getId())
            .count();
        System.out.println(c.getId() + ". " + c.getName() + " (" + postCount + "个帖子)");
    }
}

public boolean updateCategory(int id, String newName) {
    Category c = categoryMap.get(id);
    if (c == null) {
        System.out.println("分类不存在");
        return false;
    }
    if (newName == null || newName.trim().isEmpty()) {
        System.out.println("名称不可为空");
        return false;
    }
    c.setName(newName);
    System.out.println("分类更新成功");
    return true;
}

public boolean deleteCategory(int id) {
    if (!categoryMap.containsKey(id)) {
        System.out.println("分类不存在");
        return false;
    }
    long count = postList.stream().filter(p -> p.getCategoryId() == id).count();
    if (count > 0) {
        System.out.println("该分类下还有" + count + "个帖子，无法删除");
        return false;
    }
    categoryMap.remove(id);
    System.out.println("分类删除成功");
    return true;
}

public void addPost(int postId, String title, String content, int categoryId) {
    if (!categoryMap.containsKey(categoryId)) {
        System.out.println("分类不存在，无法发布帖子");
        return;
    }
    postList.add(new Post(postId, title, content, categoryId));
    System.out.println("帖子发布成功，标题：" + title);
}

public class ForumApp {
    public static void main(String[] args) {
        CategoryService service = new CategoryService();
        Scanner scanner = new Scanner(System.in);
<pre class='brush:java;toolbar:false;'>    while (true) {
        System.out.println("\n--- 论坛分类管理 ---");
        System.out.println("1. 添加分类");
        System.out.println("2. 查看分类");
        System.out.println("3. 修改分类");
        System.out.println("4. 删除分类");
        System.out.println("5. 发布帖子");
        System.out.println("0. 退出");
        System.out.print("请选择操作：");

        int choice = scanner.nextInt();
        scanner.nextLine(); // 消费换行

        switch (choice) {
            case 1:
                System.out.print("输入分类名：");
                String name = scanner.nextLine();
                service.addCategory(name);
                break;
            case 2:
                service.listCategories();
                break;
            case 3:
                System.out.print("输入分类ID：");
                int updateId = scanner.nextInt();
                scanner.nextLine();
                System.out.print("输入新名称：");
                String newName = scanner.nextLine();
                service.updateCategory(updateId, newName);
                break;
            case 4:
                System.out.print("输入要删除的分类ID：");
                int delId = scanner.nextInt();
                service.deleteCategory(delId);
                break;
            case 5:
                System.out.print("帖子ID：");
                int postId = scanner.nextInt();
                scanner.nextLine();
                System.out.print("标题：");
                String title = scanner.nextLine();
                System.out.print("内容：");
                String content = scanner.nextLine();
                System.out.print("分类ID：");
                int catId = scanner.nextInt();
                service.addPost(postId, title, content, catId);
                break;
            case 0:
                System.out.println("退出系统");
                return;
            default:
                System.out.println("无效选择");
        }
    }
}