int NO_URL_IN_QUEUE = 4;

    /** Constant indicating that the crawler is waiting for new URLs. */
    int WAIT_NEW_URL = 8;

    /**
     * Introduces a delay based on the specified type.
     *
     * @param type the type of delay to be introduced
     */
    void delay(int type);

 * default} methods. Specifically, it forwards calls only for methods that existed <a
 * href="https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ConcurrentMap.html">before
 * {@code default} methods were introduced</a>. For newer methods, like {@code forEach}, it inherits
 * their default implementations. When those implementations invoke methods, they invoke methods on
 * the {@code ForwardingConcurrentMap}.
 *
 * @author Charles Fry

 * default} methods. Specifically, it forwards calls only for methods that existed <a
 * href="https://docs.oracle.com/javase/7/docs/api/java/util/ListIterator.html">before {@code
 * default} methods were introduced</a>. For newer methods, like {@code forEachRemaining}, it
 * inherits their default implementations. When those implementations invoke methods, they invoke
 * methods on the {@code ForwardingListIterator}.
 *

 * default} methods. Specifically, it forwards calls only for methods that existed <a
 * href="https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ConcurrentMap.html">before
 * {@code default} methods were introduced</a>. For newer methods, like {@code forEach}, it inherits
 * their default implementations. When those implementations invoke methods, they invoke methods on
 * the {@code ForwardingConcurrentMap}.
 *
 * @author Charles Fry

   *
   * <p><b>Note:</b> this method is now unnecessary and should be treated as deprecated; use {@link
   * java.util.Objects#equals} instead.
   */
  @SuppressWarnings("InlineMeSuggester") // would introduce fully qualified references to Objects
  public static boolean equal(@Nullable Object a, @Nullable Object b) {
    return java.util.Objects.equals(a, b);
  }

  /**

import com.google.common.annotations.J2ktIncompatible;
import com.google.common.collect.ImmutableMultimap;
import com.google.common.util.concurrent.Service.State;

/**
 * Superinterface of {@link ServiceManager} to introduce a bridge method for {@code
 * servicesByState()}, to ensure binary compatibility with older Guava versions that specified
 * {@code servicesByState()} to return {@code ImmutableMultimap}.
 */
@J2ktIncompatible

   */
  @JvmField val minimumConcurrentCalls: Int = 0,
  /** How long to wait to retry pre-emptive connection attempts that fail. */
  @JvmField val backoffDelayMillis: Long = 60 * 1000,
  /** How much jitter to introduce in connection retry backoff delays */
  @JvmField val backoffJitterMillis: Int = 100,

     * indirection.
     *
     * One thing to *avoid* is a change to make each Logger user use memoizingSupplier directly:
     * That may introduce an extra class for each lambda (currently a dozen).
     */
    Logger local = logger;
    if (local != null) {
      return local;
    }
    synchronized (lock) {
      local = logger;
      if (local != null) {

import com.google.common.annotations.J2ktIncompatible;
import com.google.common.collect.ImmutableMultimap;
import com.google.common.util.concurrent.Service.State;

/**
 * Superinterface of {@link ServiceManager} to introduce a bridge method for {@code
 * servicesByState()}, to ensure binary compatibility with older Guava versions that specified
 * {@code servicesByState()} to return {@code ImmutableMultimap}.
 */
@J2ktIncompatible

- Get working code on a personal branch with tests before you submit a PR.
- OkHttp is a small and light dependency.  Don't introduce new dependencies or major new functionality.