如何用java获取Json的值

String jsonStr = {"returnObj":[{"oodweek":1,"week":1},{"oodweek":1,"week":4},{"oodweek":2,"week":5}],"success":true,"msg":"欢迎来到Android的世界"} JSONObject json = new JSONObject(jsonStr);
哪位大神教下该如何获取returnObj里面的每个week的值 用java代码实现。。。。摆脱了，搞了好几个小时都没有搞定！！！
已解决。。

JSONObject json = new JSONObject(jsonStr);
String jsonarry = json.getString("returnObj");
JSONArray jsonarr = new JSONArray(jsonarry);
String str = jsonarr.get(0).toString();
json = new JSONObject(str);
String week = json.getString("week");