使用URL时无法解决符号错误

class background_thread extends AsyncTask<String ,String , Boolean > {

    protected Boolean doInBackground(String... params) {

        String UR = "127.0.0.1/abc/index.php";
        try {
            URL url = new URL(UR);
        } catch(MalformedURLException e) {
            e.printStackTrace();
        }

        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
    }

}
class background_thread extends AsyncTask<Strin