code: public long getTimeFor(int player) {
          TrackPositionUpdate update = positions.get(player);
          if (update != null) {
              return interpolateTimeSinceUpdate(update, System.nanoTime());
          }
          return  -1;  // We don't know.
      }
docs: Get the best guess we have for the current track position on the specified player.
  
  @param player the player number whose position is desired
  
  @return the milliseconds into the track that we believe playback has reached, or -1 if we don't know
  
  @throws IllegalStateException if the TimeFinder is not running