import java.util.List;
public interface AbstractTreeNode {
    // 子級(jí)id
    Long getId();
    // 父級(jí)id
    Long getParentId();
    // 子級(jí)數(shù)組
    void setChildren(List<? extends AbstractTreeNode> children);
}

import cn.bunny.tree.AbstractTreeNode;
import lombok.Data;
import java.util.List;
@Data
public class ForumBoardVo implements AbstractTreeNode {
    private Long id;
    // 父級(jí)板塊ID
    private Long parentId;
    // 板塊名
    private String boardName;
    // 封面
    private String cover;
    // 描述
    private String boardDesc;
    // 排序
    private Integer sort;
    // 0:只允許管理員發(fā)帖 1:任何人可以發(fā)帖
    private Boolean postType;
    private List<ForumBoardVo> children;
    @Override
    public void setChildren(List<? extends AbstractTreeNode> children) {
        this.children = (List<ForumBoardVo>) children;
    }
}

import java.util.ArrayList;
import java.util.List;
public class TreeBuilder<T extends AbstractTreeNode> {
    /**
     * 構(gòu)建屬性結(jié)構(gòu)
     *
     * @param nodeList 需要構(gòu)建的數(shù)組
     * @return 樹型結(jié)構(gòu)
     */
    public List<T> buildTree(List<T> nodeList) {
        List<T> tree = new ArrayList<>();
        for (T node : nodeList) {
            if (node.getParentId() == 0) {
                node.setChildren(getChildren(node.getId(), nodeList));
                tree.add(node);
            }
        }
        return tree;
    }
    /**
     * 遞歸設(shè)置子級(jí)菜單
     *
     * @param nodeId   節(jié)點(diǎn)id
     * @param nodeList 節(jié)點(diǎn)列表
     * @return 子級(jí)菜單
     */
    private List<T> getChildren(Long nodeId, List<T> nodeList) {
        List<T> children = new ArrayList<>();
        for (T node : nodeList) {
            if (node.getParentId().equals(nodeId)) {
                node.setChildren(getChildren(node.getId(), nodeList));
                children.add(node);
            }
        }
        return children;
    }
}

public List<ForumBoardVo> loadBoard() {
    // 數(shù)據(jù)庫中l(wèi)ist
    List<ForumBoard> forumBoardListDB = list();
    // 構(gòu)建返回對(duì)象數(shù)組
    List<ForumBoardVo> forumBoardVoList = new ArrayList<>();
    // 樹型結(jié)構(gòu)返回?cái)?shù)組
    TreeBuilder<ForumBoardVo> treeBuilder = new TreeBuilder<>();
    // 對(duì)數(shù)據(jù)庫中數(shù)組進(jìn)行排序，這個(gè)可有可無
    forumBoardListDB.sort(Comparator.comparing(ForumBoard::getSort));
    // 將數(shù)據(jù)庫中數(shù)組一個(gè)一個(gè)塞到 List<ForumBoardVo> 的數(shù)組中
    forumBoardListDB.forEach(forumBoard -> {
        ForumBoardVo forumBoardVo = new ForumBoardVo();
        BeanUtils.copyProperties(forumBoard, forumBoardVo);
        forumBoardVoList.add(forumBoardVo);
    });
    // 最后將調(diào)用樹形結(jié)構(gòu)對(duì)象，構(gòu)建樹型結(jié)構(gòu)。
    return treeBuilder.buildTree(forumBoardVoList);
}