* return null; // Didn't find a preemptive auth scheme.
 * ```
 *
 * ## Reactive Authentication
 *
 * Implementations authenticate by returning a follow-up request that includes an authorization
 * header, or they may decline the challenge by returning null. In this case the unauthenticated
 * response will be returned to the caller that triggered it.
 *
 * Implementations should check if the initial request already included an attempt to

 *
 * Each entry is 4 bytes, and represents a _range_ of code points that all share a common 14-bit
 * prefix. Entries are sorted by their complete code points.
 *
 * The 4 bytes are named b0, b1, b2 and b3. We also define these supplemental values:
 *
 *  * **b2a**: b2 + 0x80
 *  * **b3a**: b3 + 0x80
 *  * **b2b3**: (b2 << 7) + b3
 *
 * b0
 * --
 *

    .addSubjectAlternativeName("localhost")
    .build();
```

[`HandshakeCertificates`][handshake_certificates] keeps the certificates for a TLS handshake.
Use its [builder][handshake_certificates_builder] to define which certificates the HTTPS server
returns to its clients. The returned instance can create an `SSLSocketFactory` that implements this
policy:

```java

    } catch (_: IllegalArgumentException) {
      defaultValue // This charset is invalid or unsupported. Give up.
    }
  }

  /**
   * Returns the parameter [name] of this media type, or null if this media type does not define
   * such a parameter.
   */
  fun parameter(name: String): String? = commonParameter(name)

  @JvmName("-deprecated_type")
  @Deprecated(
    message = "moved to val",

SAM Conversions
---------------

When you use Java APIs from Kotlin you can operate on Java interfaces as if they were Kotlin
lambdas. The [feature][java_sams] is available for interfaces that define a Single Abstract Method
(SAM).

But when you use Kotlin APIs from Kotlin there’s no automatic conversion. Code that used SAM lambdas
with OkHttp 3.x: must use `object :` with OkHttp 4.x:

Kotlin calling OkHttp 3.x:

  @ValueSource(booleans = [false, true])
  fun proxyMoveTest(cleanShutdown: Boolean) {
    // Define a single Proxy at myproxy:8008 that will artificially move during the test
    val proxySelector = RecordingProxySelector()
    proxySelector.proxies.add(Proxy(Proxy.Type.HTTP, InetSocketAddress("myproxy", 8008)))

    // Define two host names for the DNS routing of fake proxy servers

    val client = makeClient()
    makeRequest(client)

    // As of OkHttp 5 we now apply the ordering from the OkHttpClient, which defaults to MODERN_TLS
    // Clients might need a changed order, but can at least define a preferred order to override that default.
    val socketOrderedByDefaults =
      handshakeEnabledCipherSuites.sortedBy { ConnectionSpec.MODERN_TLS.cipherSuitesAsString!!.indexOf(it) }

```kotlin
    dependencies {
       // define a BOM and its version
       implementation(platform("com.squareup.okhttp3:okhttp-bom:4.12.0"))

       // define any required OkHttp artifacts without version
       implementation("com.squareup.okhttp3:okhttp")
       implementation("com.squareup.okhttp3:logging-interceptor")

`MultipartBody.Builder` can build sophisticated request bodies compatible with HTML file upload forms. Each part of a multipart request body is itself a request body, and can define its own headers. If present, these headers should describe the part body, such as its `Content-Disposition`. The `Content-Length` and `Content-Type` headers are added automatically if they're available.

    open fun headers(headers: Headers) = commonHeaders(headers)

    /**
     * Sets this request's `Cache-Control` header, replacing any cache control headers already
     * present. If [cacheControl] doesn't define any directives, this clears this request's
     * cache-control headers.
     */
    open fun cacheControl(cacheControl: CacheControl): Builder = commonCacheControl(cacheControl)