我正在使用下面的代码从url读取一个页面源代码(https://www.amazon.com)在netbeans中使用“utf-8”字符集，但它返回未知字符（附带的图像）。我不知道是什么问题，如果你能帮我修改代码使之正常工作，我将不胜感激？谢谢。

public static String getURLSource(String url) throws IOException
{
    URL urlObject = new URL(url);
    URLConnection urlConnection = urlObject.openConnection();
    urlConnection.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.95 Safari/537.11");
    return toString(urlConnection.getInputStream());
}
private static String toString(InputStream inputStream) throws IOException
{
    try (BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream, "UTF-8")))
    {
        String inputLine;
        StringBuilder stringBuilder = new StringBuilder();
        while ((inputLine = bufferedReader.readLine()) != null)
        {
            stringBuilder.append(inputLine);
        }
        return stringBuilder.toString();
    }
}