提前循环一遍所有节点，将父子关系保持在map里

public String buildUserDistrictTree(List
    
      districts){				//三级		Map
     
      >  map=new HashMap
      
       >();		for(EypArea eypArea : districts){			if (map.get(eypArea.getParentId())!=null) {				map.get(eypArea.getParentId()).add(eypArea);			}else {				map.put(eypArea.getParentId(), new ArrayList
       
        ());				map.get(eypArea.getParentId()).add(eypArea);			}		} 				List
        
          roots=map.get("0");		Collections.sort(roots, new Comparator
         
          (){ @Override public int compare(EypArea o1, EypArea o2) { return o1.getId().compareTo(o2.getId()); } }); String tree=scmOrganizationService.buildDistrictsTreeWithCashMap(roots, map); return tree; }public String buildDistrictsTreeWithCashMap(List
          
            rootList,Map
           
            > eypAreaMap){ Stack
            
              stack=new Stack
             
              (); JSONArray roots=JSONArray.fromObject(rootList); for (int i = 0; i < roots.size(); i++) { stack.push(roots.getJSONObject(i)); } while (!stack.isEmpty()) { JSONObject parent=stack.pop(); if (ParameterUtils.hasItem(eypAreaMap.get(parent.getString("id")))) { JSONArray jsonArray=JSONArray.fromObject(eypAreaMap.get(parent.getString("id"))); parent.put("children", jsonArray); parent.put("spread", false); jsonArray=parent.getJSONArray("children"); for (int i = 0; i < jsonArray.size(); i++) { stack.push(jsonArray.getJSONObject(i)); } } } return roots.toString(); }