In my Android app, I'm trying to check if an IBAN bank account number is valid. This supposedly can be done using the Apache IBANCheckDigit. I now try do so as follows:

IBANCheckDigit a = new IBANCheckDigit();
try {
    String checkDigit = a.calculate("MY_IBAN_NUMBER_HERE");
    Boolean b = a.isValid(checkDigit);
    Log.e("isValid: ", b.toString());
} catch (CheckDigitException e) {
    Log.e(this, "THIS IS AN ERROR");
}

This however, always prints false. Even if I insert my own (correct) IBAN-number, it also gives a false.

Does anybody know how to use this Apache IBANCheckDigit? Any tips are welcome!