}
            return new SpnegoCredential(username[0]);
        }).orElse(null);

    }

    /**
     * SPNEGO filter configuration implementation.
     *
     * This inner class provides configuration parameters for the SPNEGO filter,
     * mapping system properties to SPNEGO configuration values. It handles
     * various authentication settings including Kerberos configuration,

   * <p><b>{@code Stream} equivalent:</b> {@link Stream#filter}.
   */
  public static <T extends @Nullable Object> Iterable<T> filter(
      Iterable<T> unfiltered, Predicate<? super T> retainIfTrue) {
    checkNotNull(unfiltered);
    checkNotNull(retainIfTrue);
    return new FluentIterable<T>() {
      @Override
      public Iterator<T> iterator() {
        return Iterators.filter(unfiltered.iterator(), retainIfTrue);
      }

   * it does.
   *
   * <p>The caller is responsible for ensuring that the returned stream is closed. For example:
   *
   * {@snippet :
   * try (Stream<String> lines = source.lines()) {
   *   lines.map(...)
   *      .filter(...)
   *      .forEach(...);
   * }
   * }
   *

   * it does.
   *
   * <p>The caller is responsible for ensuring that the returned stream is closed. For example:
   *
   * {@snippet :
   * try (Stream<String> lines = source.lines()) {
   *   lines.map(...)
   *      .filter(...)
   *      .forEach(...);
   * }
   * }
   *

   * <p><b>{@code Stream} equivalent:</b> {@link Stream#filter}.
   */
  public static <T extends @Nullable Object> Iterable<T> filter(
      Iterable<T> unfiltered, Predicate<? super T> retainIfTrue) {
    checkNotNull(unfiltered);
    checkNotNull(retainIfTrue);
    return new FluentIterable<T>() {
      @Override
      public Iterator<T> iterator() {
        return Iterators.filter(unfiltered.iterator(), retainIfTrue);
      }

    }

    /**
     * Adds a filter to the query processing chain.
     * The filter chain is recreated after adding the filter.
     *
     * @param filter the filter to add
     */
    public void addFilter(final Filter filter) {
        filterList.add(filter);
        createFilterChain();
    }

    /**
     * Creates the filter chain by combining all registered filters.

 * relevant methods below.
 *
 * <ul>
 *   <li>This class is serializable; {@code java.util.Optional} is not.
 *   <li>{@code java.util.Optional} has the additional methods {@code ifPresent}, {@code filter},
 *       {@code flatMap}, and {@code orElseThrow}.
 *   <li>{@code java.util} offers the primitive-specialized versions {@code OptionalInt}, {@code

        // Verify iteration
        assertTrue(iterator.hasNext());
        assertSame(resource, iterator.next());
        assertFalse(iterator.hasNext());

        // With filter, resource should be closed due to try-with-resources
        verify(filter).accept(resource);
        verify(resource).close();
    }

    @Test
    @DisplayName("Iterator with rejecting filter - finds next acceptable")

        assertFalse(filter(createUnfiltered(contents), EVEN).contains(new Object()));
      }
    }

    public void testAddAllFailsAtomically() {
      ImmutableList<Integer> toAdd = ImmutableList.of(2, 4, 3);
      for (List<Integer> contents : SAMPLE_INPUTS) {
        C filtered = filter(createUnfiltered(contents), EVEN);
        C filteredToModify = filter(createUnfiltered(contents), EVEN);

    // In the process we made one successful connection attempt.
    assertThat(eventRecorder.recordedEventTypes().filter { it == ConnectStart::class }).hasSize(2)
    assertThat(eventRecorder.recordedEventTypes().filter { it == ConnectFailed::class }).hasSize(1)
    assertThat(eventRecorder.recordedEventTypes().filter { it == ConnectEnd::class }).hasSize(1)
  }

  @Test
  fun reachesIpv6WhenIpv4IsDown() {
    serverIpv4.close()