route: Route?,
            response: Response,
          ): Request? {
            if (response.request.header("Authorization") != null) {
              return null // Give up, we've already attempted to authenticate.
            }

            println("Authenticating for response: $response")
            println("Challenges: ${response.challenges()}")

    ```kotlin
    if (credential == response.request.header("Authorization")) {
      return null // If we already failed with these credentials, don't retry.
     }
    ```

    You may also skip the retry when you’ve hit an application-defined attempt limit:

import com.google.caliper.BeforeExperiment;
import com.google.caliper.Benchmark;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;

/**
 * Benchmark for HashMultiset.add for an already-present element.
 *
 * @author Louis Wasserman
 */
public class HashMultisetAddPresentBenchmark {
  private static final int ARRAY_MASK = 0x0ffff;
  private static final int ARRAY_SIZE = 0x10000;

  public Authenticate() {
    client = new OkHttpClient.Builder()
        .authenticator((route, response) -> {
          if (response.request().header("Authorization") != null) {
            return null; // Give up, we've already attempted to authenticate.
          }

          System.out.println("Authenticating for response: " + response);
          System.out.println("Challenges: " + response.challenges());

       *   user task -- which means that we already got past this code (or else we exited early
       *   above))
       */
      // Unconditionally set; there is no risk of throwing away a queued task from another thread,
      // because in order for the current task to run on this executor the previous task must have
      // already started execution. Because each task on a TaskNonReentrantExecutor can only produce

import com.google.caliper.BeforeExperiment;
import com.google.caliper.Benchmark;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;

/**
 * Benchmark for HashMultiset.add for an already-present element.
 *
 * @author Louis Wasserman
 */
public class HashMultisetAddPresentBenchmark {
  private static final int ARRAY_MASK = 0x0ffff;
  private static final int ARRAY_SIZE = 0x10000;

	return e.Bucket + " invalid bucket name error: " + e.Err.Error()
}

func (e Error) Error() string {
	return "dns related error: " + e.Err.Error()
}

// ErrBucketConflict for buckets that already exist
type ErrBucketConflict Error

func (e ErrBucketConflict) Error() string {
	return e.Bucket + " bucket conflict error: " + e.Err.Error()
}

// Store dns record store
type Store interface {

// roundtrip performs a roundtrip, returning the first response.
// This cannot be used concurrently.
func (m *muxClient) roundtrip(h HandlerID, req []byte) ([]byte, error) {
	if m.init {
		return nil, errors.New("mux client already used")
	}
	m.init = true
	m.singleResp = true
	msg := message{
		Op:         OpRequest,
		MuxID:      m.MuxID,
		Handler:    h,
		Flags:      m.BaseFlags | FlagEOF,
		Payload:    req,

  override fun cancel() {
    if (canceled) return // Already canceled.

    canceled = true
    exchange?.cancel()
    for (plan in plansToCancel) {
      plan.cancel()
    }

    eventListener.canceled(this)
  }

  override fun isCanceled(): Boolean = canceled

  override fun execute(): Response {
    check(executed.compareAndSet(false, true)) { "Already Executed" }

    timeout.enter()

                ? makeImmutable(entry, key, value)
                : new NonTerminalImmutableMapEntry<K, V>(key, value, keyBucketHead);
        table[tableIndex] = effectiveEntry;
      } else {
        // We already saw this key, and the first value we saw (going backwards) is the one we are
        // keeping. So we won't touch table[], but we do still want to add the existing entry that