// Fail fast on a null. We throw NPE here because the contract of Executor states that it throws
    // NPE on null listener, so we propagate that contract up into the add method as well.
    checkNotNull(runnable, "Runnable was null.");
    checkNotNull(executor, "Executor was null.");

    // Lock while we check state. We must maintain the lock while adding the new pair so that

    return lock.getHoldCount();
  }

  /**
   * Returns an estimate of the number of threads waiting to enter this monitor. The value is only
   * an estimate because the number of threads may change dynamically while this method traverses
   * internal data structures. This method is designed for use in monitoring of the system state,
   * not for synchronization control.
   */
  public int getQueueLength() {

    // Fail fast on a null. We throw NPE here because the contract of Executor states that it throws
    // NPE on null listener, so we propagate that contract up into the add method as well.
    checkNotNull(runnable, "Runnable was null.");
    checkNotNull(executor, "Executor was null.");

    // Lock while we check state. We must maintain the lock while adding the new pair so that

   * result of the query. Or use {@code LoadingCache.get(K)}, which lacks the ability to refer to
   * state other than that in the key.
   *
   * <p><b>Warning:</b> as with {@link CacheLoader#load}, {@code loader} <b>must not</b> return
   * {@code null}; it may either return a non-null value or throw an exception.
   *
   * <p>No observable state associated with this cache is modified until loading completes.
   *

 * [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.

              + this
              + " to reach a terminal state. "
              + "Current state: "
              + state());
    }
  }

  /** Checks that the current state is equal to the expected state. */
  @GuardedBy("monitor")
  private void checkCurrentState(State expected) {
    State actual = state();
    if (actual != expected) {
      if (actual == FAILED) {

    state = STATE_WRITING_REQUEST_BODY
    return ChunkedSink()
  }

  private fun newKnownLengthSink(): Sink {
    check(state == STATE_OPEN_REQUEST_BODY) { "state: $state" }
    state = STATE_WRITING_REQUEST_BODY
    return KnownLengthSink()
  }

  private fun newFixedLengthSource(
    url: HttpUrl,
    length: Long,
  ): Source {
    check(state == STATE_OPEN_RESPONSE_BODY) { "state: $state" }

 * operations. A partially-reclaimed entry is never exposed to the user. Any {@link Map.Entry}
 * instance retrieved from the map's {@linkplain Map#entrySet entry set} is a snapshot of that
 * entry's state at the time of retrieval; such entries do, however, support {@link
 * Map.Entry#setValue}, which simply calls {@link Map#put} on the entry's key.
 *

      for any such Derivative Works as a whole, provided Your use,
      reproduction, and distribution of the Work otherwise complies with
      the conditions stated in this License.

   5. Submission of Contributions. Unless You explicitly state otherwise,
      any Contribution intentionally submitted for inclusion in the Work
      by You to the Licensor shall be under the terms and conditions of

     *
     * @throws NullPointerException if {@code key}, {@code values}, or any element in {@code values}
     *     is null. The builder is left in an invalid state.
     */
    @CanIgnoreReturnValue
    public Builder<K, V> putAll(K key, Iterable<? extends V> values) {
      if (key == null) {