Don’t use the getJsonObject()
method to get the values inside the JSONObject, but use the corresponding getters for the types of the values. The key-value pairs themselves are no JSONObjects.
JSONObject jsonObj = new JSONObject(response);
String fromCurrency = jsonObj.getString("from");
String toCurrency= jsonObj.getJSONObject("to");
Double fromAmount = jsonObj.getDouble("from_amount");
Double toAmount= jsonObj.getDouble("to_amount");
solved How to read json with this format