*/
    public void addUrl(final RequestData url) {
        childUrlSet.add(url);
    }

    /**
     * Add child URLs.
     * @param c the collection of request data to add to the child URL set
     */
    public void addAllUrl(final Collection<RequestData> c) {
        if (c != null) {
            childUrlSet.addAll(c);
        }
    }

    /**

                                final String[] values = metadata.getValues(name);
                                if (values != null) {
                                    Collections.addAll(list, values);
                                }
                            }
                        }
                        if (!list.isEmpty()) {

     */
    public synchronized void addUrlQueueList(final String sessionId, final Queue<UrlQueueImpl<Long>> urlQueueList) {
        final Queue<UrlQueueImpl<Long>> uqList = getUrlQueueList(sessionId);
        uqList.addAll(urlQueueList);
        urlQueueMap.put(sessionId, uqList);
    }

    /**
     * Removes the URL queue for the specified session ID.
     * @param sessionId the session ID
     */

                if (isNewUrl(urlQueue, urlQueueList)) {
                    targetList.add(urlQueue);
                }
            }
            urlQueueList.addAll(targetList);
        }

    }

    /**
     * Checks if a URL is new.
     *
     * @param urlQueue The URL queue.
     * @param urlQueueList The list of URL queues.

                    } catch (final Exception e) {
                        throw new OpenSearchAccessException("Failed to delete " + urlQueueList, e);
                    }
                }

                waitingQueue.addAll(urlQueueList);

                urlQueue = waitingQueue.poll();
                if (urlQueue == null) {
                    return null;
                }
            }

        }

                        }
                        return new BasicNameValuePair(name, value);
                    }).collect(Collectors.toList()));
            if (paramList != null) {
                parameters.addAll(
                        paramList.stream().map(p -> new BasicNameValuePair(p.getFirst(), p.getSecond())).collect(Collectors.toList()));
            }
            return new UrlEncodedFormEntity(parameters, encoding);

```java
// Create multiple crawler instances
Crawler crawler1 = container.getComponent("crawler");
crawler1.setSessionId("session1");
crawler1.addUrl("https://site1.com");

Crawler crawler2 = container.getComponent("crawler");  
crawler2.setSessionId("session2");
crawler2.addUrl("https://site2.com");

// Execute concurrently
crawler1.setBackground(true);
crawler2.setBackground(true);

            file.delete();
            file.mkdirs();
            file.deleteOnExit();
            fileTransformer.setPath(file.getAbsolutePath());
            crawler.addUrl(url);
            crawler.crawlerContext.setMaxAccessCount(maxCount);
            crawler.crawlerContext.setNumOfThread(numOfThread);
            crawler.urlFilter.addInclude(url + ".*");

            file.delete();
            file.mkdirs();
            file.deleteOnExit();
            fileTransformer.setPath(file.getAbsolutePath());
            crawler.addUrl(url);
            crawler.crawlerContext.setMaxAccessCount(maxCount);
            crawler.crawlerContext.setNumOfThread(numOfThread);
            crawler.urlFilter.addInclude(url + ".*");

            file.delete();
            file.mkdirs();
            file.deleteOnExit();
            fileTransformer.setPath(file.getAbsolutePath());
            crawler.addUrl(url);
            crawler.getCrawlerContext().setMaxAccessCount(maxCount);
            crawler.getCrawlerContext().setNumOfThread(numOfThread);
            crawler.urlFilter.addInclude(url + ".*");