页面报数组V is null

public String getCrewCostComparison(String currentMonthlyTime) {

  Map<String,Object> result = service.getCrewCostComparison(currentMonthlyTime);
 
if(service.getCrewCostComparison(currentMonthlyTime)!=null&&!result.get("rows").toString().equals("[null]"))
{
System.out.println("_______" + result.size() + result.get("rows"));
return JSONObject.fromObject(result).toString();
}
else
{
return "";
}

只需如红色部分将 result这个map结果集进行判断，如果结果集为空，则放回字符串“”，就不会在页面报数组V is null