* that controls the interval between requests to the same host.
 * It uses a ConcurrentMap to store the last access time for each host.
 * The delayBeforeProcessing method is overridden to introduce a delay before processing a URL,
 * ensuring that requests to the same host are not made too frequently.
 * The delay is calculated based on the configured delayMillisBeforeProcessing parameter.

 *
 * <p>
 * This class defines the contract for delaying the crawling process at various points, such as:
 * </p>
 * <ul>
 *   <li>Before processing a URL ({@link #delayBeforeProcessing()})</li>
 *   <li>After processing a URL ({@link #delayAfterProcessing()})</li>
 *   <li>When there are no URLs in the queue ({@link #delayAtNoUrlInQueue()})</li>

            ThreadUtil.sleep(delayMillisAtNoUrlInQueue);
        }
    }

    /**
     * Delays before processing a URL.
     */
    @Override
    protected void delayBeforeProcessing() {
        if (delayMillisBeforeProcessing > 0) {
            ThreadUtil.sleep(delayMillisBeforeProcessing);
        }
    }

    /**
     * Delays for waiting for new URLs.
     */

     */
    private static class TestIntervalController implements IntervalController {
        @Override
        public void delay(int type) {
        }

        public void delayBeforeProcessing() {
        }

        public void delayAfterProcessing() {
        }

        public void delayAtNoUrlInQueue() {
        }

        public void delayForWaitingNewUrl() {
        }