code: @Override
  	protected String initValuesImpl(final FieldCase c) throws Exception {
  		if (c == FieldCase.NULL) {
  			return null;
  		}
  		if (c != null || isMandatory() || choice.isNext()) {
  			return constraint.initValues(c);
  		}
  		return constraint.initValues(FieldCase.NULL);
  	}
docs: If the passed FieldCase equals {@link FieldCase#NULL}, {@code null} is returned. If
  {@link #isMandatory()} is {@code true} the field value is generated depending on the
  Fieldcase. If the {@link #isMandatory()} is {@code false} the constraint value is generated
  for only half the cases.