public void joinChannel(String channel){
  Set<String> channels=new HashSet<>();
  channels.add(channel);
  joinChannels(channels);
}

public void joinChannel ( String channel ) { Set < String > channels = new HashSet < > ( ) ; channels . add ( channel ) ; joinChannels ( channels ) ; }
joins the channel with the given name , but only if the channel name is deemed valid , it ' s possible to join channels at this point and we are not already on the channel .
