class BlacklistValidation implements FormItemValidation<Object> {

    @Override
    public ValidationResult validate(final Object value) {
        if (value == null || String.valueOf(value).trim().length() == 0) {
            return ValidationResult.OK;
        } else {
            //noinspection SuspiciousMethodCalls
            return blacklist.contains(value) ? ValidationResult.invalid(errorMessage()) : ValidationResult.OK;
        }
    }

    public  BlacklistValidation(final String first, final String... rest);
    public  BlacklistValidation(Iterable<String> blacklist);

}