Cannot resolve symbol HttpGet,HttpClient,HttpResponce in Android Studio

final String ERROR = "my error message....";

 private class DownloadWebPageTask extends AsyncTask<String, Void, String> {
// some code and method ..... see AsyncTask

       @Override
        protected String doInBackground(String... urls) {

              URL urlL = null;
                try {
                    urlL = new URL(url);//"//chmi.cz..../"
                    HttpURLConnection urlConnection = null;
                    try {
                         urlConnection = (HttpURLConnection) urlL.openConnection();
                        InputStream in = new BufferedInputStream(urlConnection.getInputStream());
                      response =  readStream(in);
                        return response;
                    } catch (IOException e) {
                        //throw new RuntimeException(e);

                    } finally {
                        if(urlConnection != null)
                            urlConnection.disconnect();
                        return ERROR;
                    }
                } catch (MalformedURLException e) {
                    e.printStackTrace();
                    return ERROR;
                }
           }
            return response;
        }

        private String readStream(InputStream is) {
            try {
                ByteArrayOutputStream bo = new ByteArrayOutputStream();
                int i = is.read();
                while(i != -1) {
                    bo.write(i);
                    i = is.read();
                }
                return bo.toString();
            } catch (IOException e) {
                return "";
            }
        }