code: protected NumberRule selectNumberRule(final int field, final int padding) {
  		switch (padding) {
  			case 1:
  				return new UnpaddedNumberField(field);
  			case 2:
  				return new TwoDigitNumberField(field);
  			default:
  				return new PaddedNumberField(field, padding);
  		}
  	}
docs: <p>
  Gets an appropriate rule for the padding required.
  </p>
  
  @param field the field to get a rule for
  @param padding the padding required
  @return a new rule with the correct padding