OkHttpClient client = new OkHttpClient.Builder()
    .addInterceptor(new LoggingInterceptor())
    .build();

Request request = new Request.Builder()
    .url("http://www.publicobject.com/helloworld.txt")
    .header("User-Agent", "OkHttp Example")
    .build();

Response response = client.newCall(request).execute();
response.body().close();
```

        .url(server.url("/"))
        .head()
        .header("User-Agent", "SyncApiTest")
        .build()
    executeSynchronously(request)
      .assertCode(200)
      .assertHeader("Content-Type", "text/plain")
    val recordedRequest = server.takeRequest()
    assertThat(recordedRequest.method).isEqualTo("HEAD")
    assertThat(recordedRequest.headers["User-Agent"]).isEqualTo("SyncApiTest")

    val parts = header.split(':', limit = 2)
    if (!isSpecialHeader(parts[0])) {
      request.header(parts[0], parts[1])
    }
  }
  referer?.let {
    request.header("Referer", it)
  }
  request.header("User-Agent", userAgent)

  return request.build()
}

private fun Main.mediaType(): MediaType? {
  val mimeType =
    headers?.let {
      for (header in it) {
        val parts = header.split(':', limit = 2)

        .method("CONNECT", null)
        .header("Host", route.address.url.toHostHeader(includeDefaultPort = true))
        .header("Proxy-Connection", "Keep-Alive") // For HTTP/1.0 proxies like Squid.
        .header("User-Agent", USER_AGENT)
        .build()

    val fakeAuthChallengeResponse =
      Response.Builder()
        .request(proxyConnectRequest)
        .protocol(Protocol.HTTP_1_1)
        .code(HttpURLConnection.HTTP_PROXY_AUTH)

 *  New: Constant string `okhttp3.VERSION`. This is a string like "4.5.0-RC1", "4.5.0", or
    "4.6.0-SNAPSHOT" indicating the version of OkHttp in the current runtime. Use this to include
    the OkHttp version in custom `User-Agent` headers.

 *  Fix: Don't crash when running as a plugin in Android Studio Canary 4.1. To enable
    platform-specific TLS features OkHttp must detect whether it's running in a JVM or in Android.

      throw RuntimeException(failure)
    }

    return countRef.get()
  }

  private fun updateReports() {
    val latch = CountDownLatch(1)
    newWebSocket(
      "/updateReports?agent=$USER_AGENT",
      object : WebSocketListener() {
        override fun onClosing(
          webSocket: WebSocket,
          code: Int,
          reason: String,
        ) {
          webSocket.close(1000, null)

    assertThat(recorded.headers["Accept"]).isEqualTo("text/plain")
    assertThat(recorded.headers["Accept-Encoding"]).isEqualTo("gzip")
    assertThat(recorded.headers["Connection"]).isNull()
    assertThat(recorded.headers["User-Agent"]!!).matches(Regex("Jetty/.*"))
  }

OkHttp may add headers that are absent from the original request, including `Content-Length`, `Transfer-Encoding`, `User-Agent`, `Host`, `Connection`, and `Content-Type`. It will add an `Accept-Encoding` header for transparent response compression unless the header is already present. If you’ve got cookies, OkHttp will add a `Cookie` header with them.

 *  Fix: Include a backwards-compatible `OkHttp-Response-Source` header with
    `OkUrlFactory `responses.
 *  Fix: Don't include a default User-Agent header in requests made with the Call
    API. Requests made with OkUrlFactory will continue to have a default user
    agent.
 *  New: Guava-like API to create headers:

    ```java
    Headers headers = Headers.of(name1, value1, name2, value2, ...).
    ```

   * by the application:
   *
   * * It may be transformed by the user's interceptors. For example, an application interceptor
   *   may add headers like `User-Agent`.
   * * It may be the request generated in response to an HTTP redirect or authentication
   *   challenge. In this case the request URL may be different than the initial request URL.
   *