about JAVA com.alibaba.fastjson.JSONObject class extends, How to correct mistake?

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!

1 Answer

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");