public URL[] getUrls() {
        URL[] urls = new URL[_elements.size()];
        int index = 0;
        for (File file : _elements) {
            try {
                urls[index++] = file.toURI().toURL();
            } catch (MalformedURLException e) {
                e.printStackTrace();
                return new URL[0];
            }
        }
        return urls;
    }