public void addPinger(Pinger pinger){
  if (!mPingers.contains(pinger)) {
    mPingers.add(pinger);
    notifyDataSetChanged();
  }
}

public void addPinger ( Pinger pinger ) { if ( ! mPingers . contains ( pinger ) ) { mPingers . add ( pinger ) ; notifyDataSetChanged ( ) ; } }
add a pinger to the list .
