java将list转为树形结构的方法
原始数据如下 [ { "name":"甘肃省", "pid":0, "id":1 }, { "name":"天水市", "pid":1, "id":2 }, { "name":"秦州区", "pid":2, "id":3 }, { "name":"北京市", "pid":0, "id":4 }, { "name":"昌平区", "pid":4, "id":5 } ] 现需要是使用java将以上数据转为树形结构,转化后下的结构如下 [ { "children":[ { "children":[ { "name":"秦州区", "pid":2, "id":3 } ], "name":"天水市", "pid":1, "id":2 } ], "name":"甘肃省", "pid":0, "id":1 }, { "children":[ { "name":"昌平区", "pid":4, "id":5 } ], "name":"北京市", "pid":0, "id":4 } ] 代码如下 /** * listToTree * <p>方法说明<p> * 将JSONArray数组转为树状结构 * @param arr 需要转化的数据 * @param id 数据唯一的标识键值 * @param pid 父id唯一标识键值 * @param child 子节点键值 * @return JSONArray */ public static JSONArray listToTree(JSONArray arr,String id,String pid,String child){ JSONArray r = new JSONArray(); JSONObject hash = new JSONObject(); //将数组转为Object的形式,key为数组中的id for(int i=0;i<arr.size();i++){ JSONObject json = (JSONObject) arr.get(i); hash.put(json.getString(id), json); } //遍历结果集 for(int j=0;j<arr.size();j++){ //单条记录 JSONObject aVal = (JSONObject) arr.get(j); //在hash中取出key为单条记录中pid的值 JSONObject hashVP = (JSONObject) hash.get(aVal.get(pid).toString()); //如果记录的pid存在,则说明它有父节点,将她添加到孩子节点的集合中 if(hashVP!=null){ //检查是否有child属性 if(hashVP.get(child)!=null){ JSONArray ch = (JSONArray) hashVP.get(child); ch.add(aVal); hashVP.put(child, ch); }else{ JSONArray ch = new JSONArray(); ch.add(aVal); hashVP.put(child, ch); } }else{ r.add(aVal); } } return r; } 测试代码如下 public static void main(String[] args){ List<Map<String,Object>> data = new ArrayList<>(); Map<String,Object> map = new HashMap<>(); map.put("id",1); map.put("pid",0); map.put("name","甘肃省"); data.add(map); Map<String,Object> map2 = new HashMap<>(); map2.put("id",2); map2.put("pid",1); map2.put("name","天水市"); data.add(map2); Map<String,Object> map3 = new HashMap<>(); map3.put("id",3); map3.put("pid",2); map3.put("name","秦州区"); data.add(map3); Map<String,Object> map4 = new HashMap<>(); map4.put("id",4); map4.put("pid",0); map4.put("name","北京市"); data.add(map4); Map<String,Object> map5 = new HashMap<>(); map5.put("id",5); map5.put("pid",4); map5.put("name","昌平区"); data.add(map5); System.out.println(JSON.toJSONString(data)); JSONArray result = listToTree(JSONArray.parseArray(JSON.toJSONString(data)),"id","pid","children"); System.out.println(JSON.toJSONString(result)); }