* @throws IllegalArgumentException if {@code duration} is negative
   * @throws IllegalStateException if {@link #refreshAfterWrite} was already set
   * @since 11.0
   */
  @GwtIncompatible // To be supported (synchronously).
  @SuppressWarnings("GoodTime") // should accept a Duration
  @CanIgnoreReturnValue
  public CacheBuilder<K, V> refreshAfterWrite(long duration, TimeUnit unit) {
    checkNotNull(unit);

- Support for query parameters, headers, body (String or stream), compression, SSL configuration, proxies, and timeouts
- Automatic in-memory or on-disk caching of request/response bodies
- Synchronous and asynchronous (callback) execution
- Minimal dependencies (only Apache Commons IO)

## Installation

### Maven

Add the dependency to your `pom.xml` (replace `x.y.z` with the latest version):

```xml
<dependency>

      // interact poorly with the reentrancy-avoiding behavior of this executor - when the operation
      // before the cancelled future completes, it will synchronously complete both the newFuture
      // from the cancelled operation and its own. This can cause one runnable to queue two tasks,
      // breaking the invariant this method relies on to iteratively run the next task after the

   */
  fun cancel()

  fun interface Factory {
    /**
     * Creates a new event source and immediately returns it. Creating an event source initiates an
     * asynchronous process to connect the socket. Once that succeeds or fails, `listener` will be
     * notified. The caller must cancel the returned event source when it is no longer in use.
     */
    fun newEventSource(

            }
        };
    }

    // ===================================================================================
    //                                                                        Asynchronous
    //                                                                        ============
    protected void async(final AsyncManager asyncManager, final Runnable runnable) {

Calls are executed in one of two ways:

 * **Synchronous:** your thread blocks until the response is readable.
 * **Asynchronous:** you enqueue the request on any thread, and get [called back](https://square.github.io/okhttp/4.x/okhttp/okhttp3/-callback/) on another thread when the response is readable.

 *
 * Other exception types cancel the current call:
 *
 *  * For synchronous calls made with [Call.execute], the exception is propagated to the caller.
 *
 *  * For asynchronous calls made with [Call.enqueue], an [IOException] is propagated to the caller
 *    indicating that the call was canceled. The interceptor's exception is delivered to the current

  @Throws(IOException::class)
  fun peekTrailers(): Headers?

  /**
   * Cancel this stream. Resources held by this stream will be cleaned up, though not synchronously.
   * That may happen later by the connection pool thread.
   */
  fun cancel()

  /**
   * Carries an exchange. This is usually a connection, but it could also be a connect plan for

     * another thread or the worker task has cleared the count and set the state.
     *
     * <p>When {@link #executor} is a directExecutor(), the value written to
     * {@code workerRunningState} will be available synchronously, and behaviour will be
     * deterministic.
     */
    @SuppressWarnings("GuardedBy")
    boolean alreadyMarkedQueued = workerRunningState != QUEUING;
    if (alreadyMarkedQueued) {
      return;
    }

 * ListenableFuture}</a>.
 *
 * <p>This class is GWT-compatible.
 *
 * <h3>Purpose</h3>
 *
 * <p>The main purpose of {@code ListenableFuture} is to help you chain together a graph of
 * asynchronous operations. You can chain them together manually with calls to methods like {@link
 * Futures#transform(ListenableFuture, com.google.common.base.Function, Executor) Futures.transform}