Java递归构建树形数据

• Java递归构建树形数据
• 一、前言
• 二、正文

• 开发工具：IntelliJ IDEA
• JDK：1.8

• 添加依赖

    org.projectlombok
    lombok
    1.18.22
    provided



    com.alibaba
    fastjson
    1.2.62

• 数据节点类： DataNode

package com.example;

import lombok.Data;
import java.util.List;


@Data
public class DataNode {
    private String id;
    private String pid; // 父节点ID
    private String name;
    private List children; // 子节点列表

    public DataNode(String id, String pid, String name) {
        this.id = id;
        this.pid = pid;
        this.name = name;
    }
}

• 树形数据工具类：TreeDataUtil

支持单根节点数据、多根节点数据和自定义单根节点数据

package com.example;

import java.util.ArrayList;
import java.util.List;


public class TreeDataUtil {

    // 数据源
    private List dataNodes = new ArrayList();
    // 默认父节点ID
    private String defaultPID = "0";

    public TreeDataUtil(List dataNodes) {
        this.dataNodes=dataNodes;
    }

    public TreeDataUtil(List dataNodes, String defaultPID) {
        this.dataNodes = dataNodes;
        this.defaultPID = defaultPID;
    }

    
    public List builSingleRootTree(){
        List treeMenus =new  ArrayList<>();
        DataNode dataNode = getSingleRootNode();
        if(dataNode != null){
            dataNode=buildChilTree(dataNode);
            treeMenus.add(dataNode);
        }
        return treeMenus;
    }

    
    public List builMultipleRootTree(){
        List treeMenus =new  ArrayList<>();
        for(DataNode dataNode : getMultipleRootNode()) {
            dataNode=buildChilTree(dataNode);
            treeMenus.add(dataNode);
        }
        return treeMenus;
    }

    
    public List builCustomSingleRootTree(String text){
        List treeMenus =new  ArrayList<>();
        DataNode dataNode = new DataNode(defaultPID, "RT01", text);
        dataNode=buildChilTree(dataNode);
        treeMenus.add(dataNode);
        return treeMenus;
    }

    
    private DataNode buildChilTree(DataNode pNode){
        List chilMenus =new  ArrayList<>();
        for(DataNode dataNode : dataNodes) {
            if(dataNode.getPid().equals(pNode.getId())) {
                // 递归查询当前节点是否还有子节点
                chilMenus.add(buildChilTree(dataNode));
            }
        }
        pNode.setChildren(chilMenus);
        return pNode;
    }

    
    private List getMultipleRootNode() {
        List roots =new  ArrayList();
        for(DataNode dataNode : dataNodes) {
            if(dataNode.getPid().equals(defaultPID)) {
                roots.add(dataNode);
            }
        }
        return roots;
    }

    
    private DataNode getSingleRootNode() {
        DataNode result = null;
        for(DataNode dataNode : dataNodes) {
            if(dataNode.getId().equals(defaultPID)) {
                result = dataNode;
                break;
            }
        }
        return result;
    }
}

• 测试类：App

package com.example;

import com.alibaba.fastjson.JSON;
import java.util.ArrayList;
import java.util.List;

public class App
{
    public static void main( String[] args )
    {
        // 测试数据
        List dataNodes= new ArrayList();
        dataNodes.add(new DataNode("0","RT01","商城"));
        dataNodes.add(new DataNode("DN001","0","电器"));
        dataNodes.add(new DataNode("DN002","0","家居"));
        dataNodes.add(new DataNode("DN011","DN001","电视"));
        dataNodes.add(new DataNode("DN012","DN001","空调"));
        dataNodes.add(new DataNode("DN013","DN001","洗衣机"));
        dataNodes.add(new DataNode("DN021","DN002","沙发"));
        dataNodes.add(new DataNode("DN021","DN002","床垫"));
        dataNodes.add(new DataNode("DN0121","DN012","美的"));
        dataNodes.add(new DataNode("DN0122","DN012","格力"));

        // 构建树形数据
        TreeDataUtil treeDataUtil =new TreeDataUtil(dataNodes);
        dataNodes=treeDataUtil.builSingleRootTree(); // 单根节点
        System.out.println(JSON.toJSONString(dataNodes));
        System.out.println("================================");
        dataNodes=treeDataUtil.builMultipleRootTree(); // 多根节点
        System.out.println(JSON.toJSONString(dataNodes));
        System.out.println("================================");
        dataNodes=treeDataUtil.builCustomSingleRootTree("根节点"); // 自定义单根节点
        System.out.println(JSON.toJSONString(dataNodes));
    }
}