Say I have this code in the AlertDialog.Builder(context) of my application. The question is in which Thread will it run?

final Thread myPrettyOperation = new Thread() {
    @Override
    public void run() {
        //Do some really long operation.
    }
};
class MyPrettyTask extends
        AsyncTask<Void, Integer, Boolean> {
    protected Boolean doInBackground(
            Void... voids) {
        myPrettyOperation.start();
        return true;
    }
    protected void onProgressUpdate(
            Integer... progress) {
    }
    protected void onPostExecute(Boolean result) {
    }
}
new MyPrettyTask().execute();