ConditionalHeadersValidator { public static ConditionalHeadersValidator of(final ValidationSettings validationSettings) { return new ConditionalHeadersValidator(requireNonNull(validationSettings), cmd -> false); } private  ConditionalHeadersValidator(final ValidationSettings validationSettings,
            final Predicate<Command<?>> additionalSkipPreconditionHeaderCheckPredicate); static ConditionalHeadersValidator of(final ValidationSettings validationSettings); static ConditionalHeadersValidator of(final ValidationSettings validationSettings,
            final Predicate<Command<?>> additionalSkipPreconditionCheckPredicate); void checkConditionalHeaders(final Command command,
            @Nullable final EntityTag currentETagValue);  }
@Test public void creationFailsWithNullValidationSettings() { assertThatExceptionOfType(NullPointerException.class) .isThrownBy(() -> ConditionalHeadersValidator.of(null)); }