Why I can not verify LinkedIn links

Question

I have to find out broken links in LinkedIn links file. I am writing code as below in Selenium Web driver but it still shows the valid links:

for (String url : linkedinURLs) {
        try {
            URL link = new URL(url);
            HttpURLConnection httpConn = (HttpURLConnection) link.openConnection();
            httpConn.setConnectTimeout(5000);
            httpConn.setInstanceFollowRedirects(true);
            httpConn.connect();

            // Get the final URL after following redirects
            String finalUrl = httpConn.getURL().toString();

            if (httpConn.getResponseCode() >= 400) {
                System.out.println("Invalid URL: " + finalUrl);
            }

            httpConn.disconnect(); // Close the connection
        } catch (IOException e) {
            // Handle any exceptions that occur during the HTTP request
            System.err.println("Error while checking URL: " + url);
            e.printStackTrace();
        }
    }