* `::1` will reach the IPv6 server.
 *
 * By orchestrating two different servers with the same port but different IP addresses, we can
 * test what OkHttp does when both are reachable, or if only one is reachable.
 *
 * This test only runs on host machines that have both IPv4 and IPv6 addresses for localhost.
 */
@Timeout(30)
class FastFallbackTest {
  @RegisterExtension

 * [okhttp-staleiferror-interceptor](https://github.com/PeelTechnologies/okhttp-staleiferror-interceptor/): serve stale responses when the server isn’t reachable.
 * [okhttp-stats](https://github.com/flipkart-incubator/okhttp-stats): Get stats like average network speed.

   *
   * <p>In an undirected graph, this is equivalent to {@link #adjacentNodes(Object)}.
   *
   * <p>This is <i>not</i> the same as "all nodes reachable from {@code node} by following outgoing
   * edges". For that functionality, see {@link Graphs#reachableNodes(Graph, Object)}.
   *
   * <p>If {@code node} is removed from the graph after this method is called, the {@code Set}

   * Specifies that each value (not key) stored in the cache should be wrapped in a {@link
   * WeakReference} (by default, strong references are used).
   *
   * <p>Weak values will be garbage collected once they are weakly reachable. This makes them a poor
   * candidate for caching; consider {@link #softValues} instead.
   *
   * <p><b>Note:</b> when this method is used, the resulting cache will use identity ({@code ==})

   */
  private static final SuccessorsFunction<Character> CYCLIC_GRAPH_CONTAINING_TREE =
      createDirectedGraph("ab", "bc", "bd", "ed", "ef", "fe");

  /**
   * A graph that is not a tree (for example, {@code h} is reachable from {@code f} via both {@code
   * e} and {@code g}) but is a valid input to {@link Traverser#forTree} when starting e.g. at node
   * {@code a} (all edges are directed facing downwards):
   *
   * {@snippet :

   * Specifies that each value (not key) stored in the cache should be wrapped in a {@link
   * WeakReference} (by default, strong references are used).
   *
   * <p>Weak values will be garbage collected once they are weakly reachable. This makes them a poor
   * candidate for caching; consider {@link #softValues} instead.
   *
   * <p><b>Note:</b> when this method is used, the resulting cache will use identity ({@code ==})

  @ParametricNullness
  public static <T extends @Nullable Object> T readLines(
      Readable readable, LineProcessor<T> processor) throws IOException {
    checkNotNull(readable);
    checkNotNull(processor);

    LineReader lineReader = new LineReader(readable);
    String line;
    while ((line = lineReader.readLine()) != null) {
      if (!processor.processLine(line)) {
        break;

          @Override
          protected void finalize() {
            latch.countDown();
          }
        };
    unused = null; // Hint to the JIT that unused is unreachable
    GcFinalization.await(latch);
    assertEquals(0, latch.getCount());
  }

  public void testAwaitDone_future() {
    SettableFuture<@Nullable Void> future = SettableFuture.create();
    Object unused =

          @Override
          protected void finalize() {
            latch.countDown();
          }
        };
    unused = null; // Hint to the JIT that unused is unreachable
    GcFinalization.await(latch);
    assertEquals(0, latch.getCount());
  }

  public void testAwaitDone_future() {
    SettableFuture<@Nullable Void> future = SettableFuture.create();
    Object unused =

        a.append(c);
        return this;
      }
    };
  }

  /** Wrap a readable in a readable to defeat any type specific optimizations. */
  private static Readable wrapAsGenericReadable(Readable a) {
    return new Readable() {
      @Override
      public int read(CharBuffer cb) throws IOException {
        return a.read(cb);
      }
    };
  }