java 实现数组树形结构

   		
            org.projectlombok
            lombok
            true
        
         
            com.alibaba
            fastjson
            1.2.58
        

import lombok.Data;

import java.util.List;

@Data
public class DemoTata {
    private String id;
    private String pid;
    private List sub;
}

		List list = new ArrayList<>();

        DemoTata demoTata1 = new DemoTata();
        demoTata1.setId("1");
        demoTata1.setPid("0");
        list.add(demoTata1);


        DemoTata demoTata2 = new DemoTata();
        demoTata2.setId("2");
        demoTata2.setPid("1");
        list.add(demoTata2);


        DemoTata demoTata3 = new DemoTata();
        demoTata3.setId("3");
        demoTata3.setPid("2");
        list.add(demoTata3);

 public void generationLevel(Map> mapData,List list){
        for(int i = 0 ; i < list.size() ; i++){
            DemoTata demoTata = list.get(i);
            String id = demoTata.getId();
            String pid = demoTata.getPid();
            List pidList = mapData.get(pid);
            if(pidList == null){
                pidList = new ArrayList<>();
            }
            pidList.add(demoTata);
            mapData.put(pid,pidList);
        }
    }

		Map> tmp_mapData = new HashMap<>();
        Set>> entries = mapData.entrySet();
        for(Map.Entry> entry : entries){
            List entryValue = entry.getValue();
            List temp_demoTatas = JSONArray.parseArray(JSON.toJSONString(entryValue), DemoTata.class);
            for(int i = 0 ; i < temp_demoTatas.size() ; i++){
                DemoTata demoTata = temp_demoTatas.get(i);
                if( mapData.get(demoTata.getId()) != null){
                    demoTata.setSub(mapData.get(demoTata.getId()));
                    temp_demoTatas.set(i,demoTata);
                }

            }
            tmp_mapData.put(entry.getKey(), temp_demoTatas);
        }

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONArray;
import org.junit.jupiter.api.Test;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class DemoTest {

    @Test
    void demotestLeve() {


        List list = new ArrayList<>();

        DemoTata demoTata1 = new DemoTata();
        demoTata1.setId("1");
        demoTata1.setPid("0");
        list.add(demoTata1);


        DemoTata demoTata2 = new DemoTata();
        demoTata2.setId("2");
        demoTata2.setPid("1");
        list.add(demoTata2);


        DemoTata demoTata3 = new DemoTata();
        demoTata3.setId("3");
        demoTata3.setPid("2");
        list.add(demoTata3);

        Map> mapData = new HashMap<>();
        Map submapData = new HashMap<>();
        generationLevel(mapData, list);

        Map> tmp_mapData = new HashMap<>();
        Set>> entries = mapData.entrySet();
        for(Map.Entry> entry : entries){
            List entryValue = entry.getValue();
            List temp_demoTatas = JSONArray.parseArray(JSON.toJSONString(entryValue), DemoTata.class);
            for(int i = 0 ; i < temp_demoTatas.size() ; i++){
                DemoTata demoTata = temp_demoTatas.get(i);
                if( mapData.get(demoTata.getId()) != null){
                    demoTata.setSub(mapData.get(demoTata.getId()));
                    temp_demoTatas.set(i,demoTata);
                }

            }
            tmp_mapData.put(entry.getKey(), temp_demoTatas);
        }


        System.out.println("list：========>"+JSON.toJSONString(list));
        System.out.println("mapData：========>"+JSON.toJSONString(mapData));
        System.out.println("tmp_mapData：========>"+JSON.toJSONString(tmp_mapData));
    }

    public void generationLevel(Map> mapData,List list){
        for(int i = 0 ; i < list.size() ; i++){
            DemoTata demoTata = list.get(i);
            String id = demoTata.getId();
            String pid = demoTata.getPid();
            List pidList = mapData.get(pid);
            if(pidList == null){
                pidList = new ArrayList<>();
            }
            pidList.add(demoTata);
            mapData.put(pid,pidList);
        }
    }
}