CSS and Image is not rendering in generated PDF - Flying Saucer

Question

I want to make a PDF for my webpage using Flying Saucer to generate a PDF. With this below code I am able to generate a PDF but without any style and css.

HTML source code,

<link rel="stylesheet" href="/css/jquery-ui.aeeab65fc7671696263825aac469a40d.css" type="text/css">
<link rel="stylesheet" href="/css/site.bc5eb8ab7795d16a0a599fbaef2adfe6.css" type="text/css">
<script src="js/sidebar.974c35aeb63e852d3fd100cc1c3ab02b.js"></script>

I am trying to set my base URL using renderer.getSharedContext().setUserAgentCallback(new NaiveUserAgent(baseUrl)) but it is not working.

Java code

try {
        // Define the URL
        String urlcheck = "http://localhost:8888/index.html";
       
        // Establish a URL connection
        HttpURLConnection connection = (HttpURLConnection) new URL(urlcheck).openConnection();
        connection.setRequestMethod("GET");

        // Set up Basic Authentication with username "admin" and password "admin"
        String username = "admin";
        String password = "admin";
        String authString = username + ":" + password;
        String encodedAuthString = Base64.getEncoder().encodeToString(authString.getBytes());

        connection.setRequestProperty("Authorization", "Basic " + encodedAuthString);

        // Check the response code (200 indicates success)
        int responseCode = connection.getResponseCode();
        if (responseCode == 200) {

          // Get the input stream from the connection
          InputStream urlInputStream = connection.getInputStream();

          LOG.info("PDF START ");
          // Create an ITextRenderer instance
          ITextRenderer renderer = new ITextRenderer();

          // Convert the InputStream to a String
          String htmlContent = convertInputStreamToString(urlInputStream);
          HtmlCleaner cleaner = new HtmlCleaner();
          TagNode rootTagNode = cleaner.clean(htmlContent);

          // set up properties for the serializer (optional, see online docs)
          CleanerProperties cleanerProperties = cleaner.getProperties();

          // use the getAsString method on an XmlSerializer class
          XmlSerializer xmlSerializer = new PrettyXmlSerializer(cleanerProperties);
          String cleanedHtml = xmlSerializer.getAsString(rootTagNode);
          LOG.info("cleanedHtml::"+cleanedHtml);

          // Set the HTML content as the document
          renderer.setDocumentFromString(cleanedHtml);

          // Render to PDF
          String baseUrl = "http://localhost:8888";
          renderer.getSharedContext().setUserAgentCallback(new NaiveUserAgent(baseUrl)); // Error

          ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
          renderer.layout();
          renderer.createPDF(outputStream);
          renderer.finishPDF();

        } else {
          LOG.error("Failed to retrieve URL content. Response code: " + responseCode);
        }
      }