R8 / ProGuard
-------------

R8 and ProGuard are both code optimizers for `.class` files.

R8 is the [default optimizer][r8] in Android Studio 3.4 and newer. It works well with all
releases of OkHttp.

ProGuard was the previous default. We’re [tracking problems][proguard_problems] with interactions
between ProGuard, OkHttp 4.x, and Kotlin-originated `.class` files. Make sure you’re on the latest

 * not</b> change the behavior of {@link #add(Object)}, which can lead to unexpected behavior. In
 * this case, you should override {@code add(Object)} as well, either providing your own
 * implementation, or delegating to the provided {@code standardAdd} method.
 *
 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code

///

An environment variable (also known as "**env var**") is a variable that lives **outside** of the Python code, in the **operating system**, and could be read by your Python code (or by other programs as well).

Environment variables could be useful for handling application **settings**, as part of the **installation** of Python, etc.

## Create and Use Env Vars { #create-and-use-env-vars }

 * <p>
 * The class uses {@link CrawlerContainer} to access components like {@link AccessResult}
 * and {@link UrlQueue}. It also uses {@link CrawlingParameterUtil} to access services
 * like {@link UrlQueueService} and DataService, as well as the {@link CrawlerContext}.
 * </p>
 *
 * <p>
 * The class provides methods to check if a response is successful or not modified based on

computer or modifying a private copy.  Propagation includes copying,
distribution (with or without modification), making available to the
public, and in some countries other activities as well.

  To "convey" a work means any kind of propagation that enables other
parties to make or receive copies.  Mere interaction with a user through
a computer network, with no transfer of a copy, is not conveying.

      }

      // If this response shouldn't have been stored, it should never be used as a response source.
      // This check should be redundant as long as the persistence store is well-behaved and the
      // rules are constant.
      if (!isCacheable(cacheResponse, request)) {
        return CacheStrategy(request, null)
      }

      val requestCaching = request.cacheControl

configured to fall back for broad connectivity.

Using OkHttp is easy. Its request/response API is designed with fluent builders and immutability. It
supports both synchronous blocking calls and async calls with callbacks.

A well behaved user agent
-------------------------

OkHttp follows modern HTTP specifications such as

* HTTP Semantics - [RFC 9110](https://datatracker.ietf.org/doc/html/rfc9110)

    void testGetNTHash_knownVector() {
        // Arrange
        String password = "password";
        // Known NT hash for "password" (UTF-16LE MD4)
        // This is a well-known test vector: password -> 8846F7EAEE8FB117AD06BDD830B7586C
        byte[] expected = hex("8846F7EAEE8FB117AD06BDD830B7586C");

        // Act
        byte[] actual = NtlmUtil.getNTHash(password);

        // Assert

        properties.put("Accept", Collections.singletonList("application/json"));
        when(mockConnection.getRequestProperties()).thenReturn(properties);
        // Need to mock getRequestProperty as well since it delegates to wrapped connection
        when(mockConnection.getRequestProperty("Accept")).thenReturn("application/json");

        // Act

     *
     * @throws IllegalArgumentException If this is not a well-formed HTTP or HTTPS URL.
     */
    @JvmStatic
    @JvmName("get")
    fun String.toHttpUrl(): HttpUrl = Builder().parse(null, this).build()

    /**
     * Returns a new `HttpUrl` representing `url` if it is a well-formed HTTP or HTTPS URL, or null
     * if it isn't.
     */
    @JvmStatic