fun interface Authenticator {
  /**
   * Returns a request that includes a credential to satisfy an authentication challenge in
   * [response]. Returns null if the challenge cannot be satisfied.
   *
   * The route is best effort, it currently may not always be provided even when logically
   * available. It may also not be provided when an authenticator is re-used manually in an

    coders call this and we don't want their users to suffer.


## Version 4.0.0

_2019-06-26_

**This release upgrades OkHttp to Kotlin.** We tried our best to make fast and safe to upgrade
from OkHttp 3.x. We wrote an [upgrade guide][upgrading_to_okhttp_4] to help with the migration and a
[blog post][okhttp4_blog_post] to explain it.

 * and initializing on first use.
 *
 * We use this because eager classpath checks cause confusion and excessive logging in Android,
 * and we can't rely on classnames after proguard, so are probably best served by falling through
 * to a situation of trying our least likely noisiest options.
 */
class DeferredSocketAdapter(private val socketAdapterFactory: Factory) : SocketAdapter {
  private var delegate: SocketAdapter? = null

   * scheduled. If the task is already in the queue, the earliest execution time is used.
   *
   * The target execution time is implemented on a best-effort basis. If another task in this queue
   * is running when that time is reached, that task is allowed to complete before this task is
   * started. Similarly the task will be delayed if the host lacks compute resources.
   *

    responseCode != HTTP_NOT_MODIFIED
  ) {
    return true
  }

  // If the Content-Length or Transfer-Encoding headers disagree with the response code, the
  // response is malformed. For best compatibility, we honor the headers.
  if (headersContentLength() != -1L ||
    "chunked".equals(header("Transfer-Encoding"), ignoreCase = true)
  ) {
    return true
  }

  return false
}

 *    number of prefixes (`us-west.www.publicobject.com`, `www.publicobject.com`) including no
 *    prefix at all (`publicobject.com`). For most applications this is the best way to configure
 *    certificate pinning.
 *
 *  * **Exactly one subdomain**: Use a single asterisk like `*.publicobject.com` to match exactly

 * the updated response if it has changed, or a short 'not modified' response if the client's copy
 * is still valid. Such responses increment both the network count and hit count.
 *
 * The best way to improve the cache hit rate is by configuring the web server to return cacheable
 * responses. Although this client honors all [HTTP/1.1 (RFC 7234)][rfc_7234] cache headers, it
 * doesn't cache partial responses.
 *

Whenever a participant has made a mistake, we expect them to take responsibility for it. If someone
has been harmed or offended, it is our responsibility to listen carefully and respectfully, and do
our best to right the wrong.

Although this list cannot be exhaustive, we explicitly honor diversity in age, culture, ethnicity,
gender identity or expression, language, national origin, political beliefs, profession, race,

          }

          connectionUser.dnsEnd(socketHost, result)
          result
        }

      // Try each address for best behavior in mixed IPv4/IPv6 environments.
      val orderedAddresses =
        when {
          fastFallback -> reorderForHappyEyeballs(addresses)
          else -> addresses
        }

 *  **OkHttp now supports prior knowledge cleartext HTTP/2.** Enable this by setting
    `Protocol.H2_PRIOR_KNOWLEDGE` as the lone protocol on an `OkHttpClient.Builder`. This mode
    only supports `http:` URLs and is best suited in closed environments where HTTPS is
    inappropriate.

 *  New: `HttpUrl.get(String)` is an alternative to `HttpUrl.parse(String)` that throws an exception