使用Gson将类和json字符串相互转换

1、从实体类到JSON字符串

      Gson gson = new Gson();
      String jsonBDID = gson.toJson(bdPushID);

2、从JSON字符串到实体类

      Gson gson = new Gson();
      BDPushID bdPushID2 = gson.fromJson(bdPushId, BDPushID.class);

3、从JSON数组到ArrayList

 Gson gson = new Gson();

Car cars = gson.fromJson(result,new TypeToken<ArrayList<Car>>() {}.getType());