code: public ArrayList<String> trackers() {
          string_vector v = p.get_trackers();
          int size = (int) v.size();
          ArrayList<String> l = new ArrayList<>();
  
          for (int i = 0; i < size; i++) {
              l.add(v.get(i));
          }
  
          return l;
      }
docs: If the torrent doesn't have a tracker, but relies on the DHT to find
  peers, the {@link #trackers(List)} can specify tracker URLs for the
  torrent.
  
  @return the list of trackers