implements PeekingIterator<T> {
    private final Queue<T> queue;

    BreadthFirstIterator(T root) {
      this.queue = new ArrayDeque<>();
      queue.add(root);
    }

    @Override
    public boolean hasNext() {
      return !queue.isEmpty();
    }

    @Override
    public T peek() {
      return queue.element();
    }

    @Override
    public T next() {

        return URL_QUEUE_THREAD_LOCAL.get();
    }

    /**
     * Sets the URL queue for the current thread. If the provided URL queue is null,
     * the URL queue for the current thread is removed.
     *
     * @param urlQueue the URL queue to be set for the current thread, or null to remove the URL queue
     */
    public static void setUrlQueue(final UrlQueue<?> urlQueue) {
        if (urlQueue == null) {

    private static final int MAX_BUFFER_SIZE = 0x100000; // 1MB maximum

    // Use concurrent queue for lock-free operations
    private static final java.util.concurrent.ConcurrentLinkedQueue<byte[]> bufferQueue =
            new java.util.concurrent.ConcurrentLinkedQueue<>();

    // Track queue size with atomic counter for efficiency

  }

  private void enqueueHelper(Event<L> event, Object label) {
    checkNotNull(event, "event");
    checkNotNull(label, "label");
    synchronized (listeners) {
      for (PerListenerQueue<L> queue : listeners) {
        queue.add(event, label);
      }
    }
  }

  /**
   * Dispatches all events enqueued prior to this call, serially and in order, for every listener.
   *

import com.google.common.annotations.GwtCompatible;
import com.google.common.collect.testing.SampleElements.Strings;
import java.util.List;
import java.util.Queue;
import org.jspecify.annotations.NullMarked;

/**
 * Create queue of strings for tests.
 *
 * @author Jared Levy
 */
@GwtCompatible
@NullMarked
public abstract class TestStringQueueGenerator implements TestQueueGenerator<String> {
  @Override

 *   <li>{@code PRE_PROCESSING} - Represents the pre-processing state.</li>
 *   <li>{@code POST_PROCESSING} - Represents the post-processing state.</li>
 *   <li>{@code NO_URL_IN_QUEUE} - Indicates that there are no URLs in the queue.</li>
 *   <li>{@code WAIT_NEW_URL} - Indicates that the crawler is waiting for new URLs.</li>
 * </ul>
 */
public interface IntervalController {
    /** Constant representing the pre-processing state. */

            errorsField.setAccessible(true);
            Queue<String> errors = (Queue<String>) errorsField.get(null);
            errors.clear();
        } catch (Exception e) {
            // Ignore if field doesn't exist
        }

        // Add some errors to the queue
        Crawler.addError("Error 1");
        Crawler.addError("Error 2");

    private final Queue<T> queue;

    UnIterableQueue(Queue<T> queue) {
      this.queue = queue;
    }

    @Override
    public Iterator<T> iterator() {
      throw new UnsupportedOperationException();
    }

    @Override
    protected Queue<T> delegate() {
      return queue;
    }
  }

  public void testIndexOf_empty() {

import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.ArrayList;
import java.util.List;

/**
 * Creates, based on your criteria, a JUnit test suite that exhaustively tests a queue
 * implementation.
 *
 * @author Jared Levy
 */
@GwtIncompatible
public final class QueueTestSuiteBuilder<E>
    extends AbstractCollectionTestSuiteBuilder<QueueTestSuiteBuilder<E>, E> {

 * and when waiting for new URLs.
 * The delays are configurable via constructor parameters.
 *
 */
public class DefaultIntervalController extends AbstractIntervalController {

    /** Delay in milliseconds after processing a URL */
    protected long delayMillisAfterProcessing = 0L;

    /** Delay in milliseconds when no URL is in the queue */