java 解决树形结构数据 （有序无序通杀）

package com.study;

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

import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;

public class SteelTree {

    public static void main(String[] args) {
        // get datas
        List<Map<String, Object>> records = getRecords();

        // Result JSON
        JSONObject result = new JSONObject();

        // record temp json
        JSONObject recordJson = new JSONObject();

        // Unknown json
        JSONObject unknownRecord = new JSONObject();

        // root id
        String firstParent = "00000";

        for (int i = 0, l = records.size(); i < l; i++) {
            Map<String, Object> record = records.get(i);

            // if parentid is null.
            String parentId;
            if (record.get("parentid") == null) {
                // TODO
                parentId = "00000";
            } else {
                parentId = record.get("parentid").toString();
            }

            // set default JSON and childern node
            JSONObject node = new JSONObject();
            node.put("id", record.get("id").toString());
            node.put("name", record.get("name").toString());
            node.put("parentid", parentId);
            node.put("children", new JSONArray());

            // if root node
            if (parentId.equals(firstParent)) {
                result.put(record.get("id").toString(), node);
                recordJson.put(record.get("id").toString(), node);

                // if parent exist
            } else if (recordJson.containsKey(parentId)) {
                // add children
                recordJson.getJSONObject(parentId).getJSONArray("children").add(node);
                recordJson.put(record.get("id").toString(), node);
                // Unknown relation node
            } else {
                String nodeId = record.get("id").toString();
                if (unknownRecord.containsKey(parentId)) {
                    // add children
                    unknownRecord.getJSONObject(parentId).getJSONArray("children").add(node);
                    recordJson.put(nodeId, node);
                } else {
                    // find subnode
                    for (Entry<String, Object> entry : unknownRecord.entrySet()) {
                        JSONObject tempNode = (JSONObject) entry.getValue();
                        if (tempNode.getString("parentid").equals(nodeId)) {
                            node.getJSONArray("children").add(tempNode);
                            recordJson.put(tempNode.get("id").toString(), tempNode);
                            unknownRecord.remove(tempNode.get("id").toString());
                            break;
                        }
                    }
                    unknownRecord.put(nodeId, node);
                }
            }
        }

        // unknownRecord add to result
        // find subnode
        for (Entry<String, Object> entry : unknownRecord.entrySet()) {
            JSONObject tempNode = (JSONObject) entry.getValue();
            String tempNodeId = tempNode.getString("parentid");
            if (recordJson.containsKey(tempNodeId)) {
                // add children
                recordJson.getJSONObject(tempNodeId).getJSONArray("children").add(tempNode);
            } else {
                // Error node
                System.out.println("========================ERROR>> " + tempNodeId + "		" + tempNode.toString());
            }
        }
        System.out.println(result.toString());
    } // End main

    private static List<Map<String, Object>> getRecords() {
        List<Map<String, Object>> result = new ArrayList<>();

        // first record
        Map<String, Object> red0101 = new HashMap<>();
        red0101.put("id", "U0003");
        red0101.put("name", "wangwu");
        red0101.put("parentid", "U0001");
        result.add(red0101);

        Map<String, Object> red010102 = new HashMap<>();
        red010102.put("id", "U0006");
        red010102.put("name", "chenba");
        red010102.put("parentid", "U0003");
        result.add(red010102);

        Map<String, Object> red01 = new HashMap<>();
        red01.put("id", "U0001");
        red01.put("name", "zhengsan");
        red01.put("parentid", "00000");
        result.add(red01);

        Map<String, Object> red02 = new HashMap<>();
        red02.put("id", "U0002");
        red02.put("name", "lisi");
        red02.put("parentid", "00000");
        result.add(red02);

        Map<String, Object> red0102 = new HashMap<>();
        red0102.put("id", "U0004");
        red0102.put("name", "zhaolu");
        red0102.put("parentid", "U0001");
        result.add(red0102);

        Map<String, Object> red010101 = new HashMap<>();
        red010101.put("id", "U0005");
        red010101.put("name", "maqi");
        red010101.put("parentid", "U0003");
        result.add(red010101);

        return result;
    }

}