code: public Token createTokenSynchronous(final Card card)
              throws AuthenticationException,
              InvalidRequestException,
              APIConnectionException,
              CardException,
              APIException {
          return createTokenSynchronous(card, mDefaultPublishableKey);
      }
docs: Blocking method to create a {@link Token}. Do not call this on the UI thread or your app
  will crash. This method uses the default publishable key for this {@link Stripe} instance.
  
  @param card the {@link Card} to use for this token
  @return a {@link Token} that can be used for this card
  
  @throws AuthenticationException failure to properly authenticate yourself (check your key)
  @throws InvalidRequestException your request has invalid parameters
  @throws APIConnectionException failure to connect to Stripe's API
  @throws CardException the card cannot be charged for some reason
  @throws APIException any other type of problem (for instance, a temporary issue with
  Stripe's servers