try {
   double temp = Double.parseDouble(str);
   double result = (option == Option.C2F)
           ? TemperatureConverter.celsiusToFahrenheit(temp)
           : TemperatureConverter.fahrenheitToCelsius(temp);
   String resultString = String.format("%.2f", result);
   destinationEditNumber.setNumber(result);
   destinationEditNumber.setSelection(resultString.length());
} catch (NumberFormatException ignore) {
   // WARNING this is generated whilst numbers are being entered,
   // for example just a '-' 
   // so we don't want to show the error just yet
} catch (Exception e) {
   sourceEditNumber.setError("ERROR: " + e.getLocalizedMessage());
}
