Android – How can I convert big number to string from jsonobject using java?

I have a response from the web service and this response is a json type string. I get the STHAR_GCMIK value here using obj.getString().

This code works correctly up to 6 digit values, but it returns 4.0E+7 for the value 4000000. I tried different solutions but failed. How can I display the value here as it is?

private AttrsSiparis parseSiparisBilgisi(String data) {
        AttrsSiparis siparisBilgileri = new AttrsSiparis();
        try {
            JSONArray jsonArray = new JSONArray(data);
            for(int i = 0; i < jsonArray.length(); i++)
            {
                JSONObject obj = jsonArray.getJSONObject(i);
                Log.i(Constants.TAG, "Irsaliye Result Parse : STHAR_GCMIK " + obj.getString("STHAR_GCMIK"));

                //siparisBilgileri.miktarlar.add(obj.getString("STHAR_GCMIK"));
                siparisBilgileri.miktarlar.add(new BigDecimal(obj.getString("STHAR_GCMIK")).toString());
                
            }
        } catch (JSONException e) {
            e.printStackTrace();
            return null;
        }
        return siparisBilgileri;
    }