关于JAVA com.alibaba.fastjson.JSONObject类的扩展，如何纠正错误？

Question

I want to extends com.alibaba.fastjson.JSONObject for new a function,follow is my code,but is wrong. how to correct mistake?

import com.alibaba.fastjson.JSONObject;
public class SJSONObject extends JSONObject 
  {
public String optString(String key) {
    if (containsKey(key)){
        return getString(key);
    }
    return "";
}
}

and then i use it:

SJSONObject jsobj  =(SJSONObject) JSON.parseObject(sb.toString());
String aa= jsobj.optString("ssss");

it is wrong!

Answer 1

You don't have to extend from JSONObject. Do something like this.

public class yourClass {

    public static String optString(JSONObject json, String key) {
        if (json.containsKey(key)){
            return json.getString(key);
        }
        else{
            return "";
        }
    }
}

and your client code can be:

JSONObject json  = new JSON.parseObject(sb.toString());
String aa= youClass.optString(json, "ssss");