*       mutable objects as elements at all, as many users may expect your "immutable" object to be
 *       <i>deeply</i> immutable.
 * </ul>
 *
 * <h4>Performance notes</h4>
 *
 * <ul>
 *   <li>Implementations can be generally assumed to prioritize memory efficiency, then speed of
 *       access, and lastly speed of creation.
 *   <li>The {@code copyOf} methods will sometimes recognize that the actual copy operation is

   * that this method will return a different number of chars than would be returned by reading all
   * of the chars.
   *
   * <p>Additionally, for mutable sources such as {@code StringBuilder}s, a subsequent read may
   * return a different number of chars if the contents are changed.
   *
   * @since 19.0
   */
  public Optional<Long> lengthIfKnown() {

   * that this method will return a different number of chars than would be returned by reading all
   * of the chars.
   *
   * <p>Additionally, for mutable sources such as {@code StringBuilder}s, a subsequent read may
   * return a different number of chars if the contents are changed.
   *
   * @since 19.0
   */
  public Optional<Long> lengthIfKnown() {

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import org.jspecify.annotations.NonNull;
import org.jspecify.annotations.Nullable;

/**
 * A mutable type-to-instance map. See also {@link ImmutableTypeToInstanceMap}.
 *
 * @author Ben Yu
 * @since 13.0
 */
public final class MutableTypeToInstanceMap<B extends @Nullable Object>

  boolean needsAllocArrays() {
    return table == null;
  }

  /** Handle lazy allocation of arrays. */
  @CanIgnoreReturnValue
  int allocArrays() {
    Preconditions.checkState(needsAllocArrays(), "Arrays already allocated");

    int expectedSize = metadata;
    int buckets = CompactHashing.tableSize(expectedSize);
    this.table = CompactHashing.createTable(buckets);

    yStats.addAll(values.yStats());
  }

  /** Returns an immutable snapshot of the current statistics. */
  public PairedStats snapshot() {
    return new PairedStats(xStats.snapshot(), yStats.snapshot(), sumOfProductsOfDeltas);
  }

  /** Returns the number of pairs in the dataset. */
  public long count() {
    return xStats.count();
  }

  /** Returns an immutable snapshot of the statistics on the {@code x} values alone. */

import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;
import org.jspecify.annotations.NonNull;
import org.jspecify.annotations.Nullable;

/**
 * A mutable class-to-instance map backed by an arbitrary user-provided map. See also {@link
 * ImmutableClassToInstanceMap}.
 *
 * <p>See the Guava User Guide article on <a href=

   * <p>Does not close the {@code Readable}. If reading files or resources you should use the {@link
   * Files#readLines} and {@link Resources#readLines} methods.
   *
   * @param r the object to read from
   * @return a mutable {@link List} containing all the lines
   * @throws IOException if an I/O error occurs
   */
  public static List<String> readLines(Readable r) throws IOException {
    List<String> result = new ArrayList<>();

    internal var method: String
    internal var headers: Headers.Builder
    internal var body: RequestBody? = null
    internal var cacheUrlOverride: HttpUrl? = null

    /** A mutable map of tags, or an immutable empty map if we don't have any. */
    internal var tags = mapOf<KClass<*>, Any>()

    constructor() {
      this.method = "GET"
      this.headers = Headers.Builder()
    }

  private lateinit var serverIpv6: MockWebServer

  private val listener = RecordingEventListener()
  private lateinit var client: OkHttpClient
  private lateinit var url: HttpUrl

  /**
   * This is mutable and order matters. By default, it contains [IPv4, IPv6]. Tests may manipulate
   * it to prefer IPv6.
   */
  private var dnsResults = listOf<InetAddress>()

  @BeforeEach
  internal fun setUp() {