json 转成 string

有个json类型的字符串 （是从别的地方拼接的）：
{"state":"1","file":
{"Bcsi01C.dll":
{"dll/Bcsi01C.dll":"1.0.0.8","lastModified":"2011-09-28 14:01:49"},
"Bcsi29C.dll":
{"dll/Bcsi29C.dll":"1.0.0.6","lastModified":"2011-09-26 13:33:34"},
"Bcsi03C.dll":
{"dll/Bcsi03C.dll":"1.0.0.4","lastModified":"2011-10-19 17:01:41"},
"Bcsi29C.dll":
{"Bcsi29C.dll":"1.0.0.6","lastModified":"2011-09-20 09:38:55"}
},
"folder":{"dll":"dll"}
}

我想拿到 里面的 Bcsi01C.dll dll/Bcsi01C.dll 1.0.0.8 lastModified 2011-09-28 14:01:49这几个类型的数据，应该怎么拿呢

JSONObject jo = JSON.parseObject(json);
JSONObject data = JSONObject.parseObject(jo.getString("Bcsi01C.dll"));
String str=data.getString("dll/Bcsi01C.dll");
String str=data.getString("lastModified");
如果不懂。去我的博客找。JSON/XML相关的。