code: public Double getDouble(final String fieldName) {
      try {
        if (_jsonObject.isNull(fieldName)) {
          return null;
        } else {
          return _jsonObject.getDouble(fieldName);
        }
      } catch (JSONException ex) {
        throw new QuandlRuntimeException("Cannot find field", ex);
      }
    }
docs: Get a Double field. This attempts to work around the stupid NaN is null behavior by explicitly testing for null. Throws a
  QuandlRuntimeException if it cannot find the field
  
  @param fieldName the name of the field
  @return the field value, or null if the field is null