*
   * @param <V1> the type returned by the first future
   * @param <V2> the type returned by the second future
   * @param <V3> the type returned by the third future
   * @param <V4> the type returned by the fourth future
   */
  public static final class Combiner4<
          V1 extends @Nullable Object,
          V2 extends @Nullable Object,
          V3 extends @Nullable Object,
          V4 extends @Nullable Object>

   *
   * @param <V1> the type returned by the first future
   * @param <V2> the type returned by the second future
   * @param <V3> the type returned by the third future
   * @param <V4> the type returned by the fourth future
   */
  public static final class Combiner4<
          V1 extends @Nullable Object,
          V2 extends @Nullable Object,
          V3 extends @Nullable Object,
          V4 extends @Nullable Object>

      )
    // Fail auth three times...
    server.enqueue(pleaseAuthenticate)
    server.enqueue(pleaseAuthenticate)
    server.enqueue(pleaseAuthenticate)
    // ...then succeed the fourth time.
    server.enqueue(
      MockResponse(body = "Successful auth!"),
    )
    java.net.Authenticator.setDefault(RecordingAuthenticator())
    client =
      client
        .newBuilder()

watch out of his pocket, and was looking at it uneasily, shaking
it every now and then, and holding it to his ear.

  Alice considered a little, and then said `The fourth.'

  `Two days wrong!' sighed the Hatter.  `I told you butter
wouldn't suit the works!' he added looking angrily at the March
Hare.

  `It was the BEST butter,' the March Hare meekly replied.