java如何通过json读取嵌套的json对象

对象数据内容如下:

{

    "str1": 11,
    "strs": [
        {
            "strs11": 111,
            "strs12": 122,
            "strs13": 133
        {
            "strs21": 211,
            "strs22": 222,
            "strs23": 233
        }
    ],
    "str2": 22,
    "str3": 33,
    "str4":44

}

关键Java代码:
    URL url = new URL("http://localhost/test.jspx");
    URLConnection urlconn = url.openConnection();
    BufferedReader reader = new BufferedReader(new InputStreamReader(urlconn.getInputStream(),"utf-8"));
    String repStr = null;
    if ((repStr = reader.readLine()) != null) {
        JSONObject jObj = JSONObject.fromObject(repStr);
        JSONArray jary=jObj.getJSONArray("strs");
        for (int i=0;i<jary.size();i++) {
            JSONObject obj = jary.getJSONObject(i);
            String s2=obj.getString("strs11");
        }

    }