private final User removeUser(String channel,String nick){
  channel=channel.toLowerCase();
  User user=new User("",nick);
synchronized (_channels) {
    Hashtable<User,User> users=_channels.get(channel);
    if (users != null) {
      return users.remove(user);
    }
  }
  return null;
}

private final User removeUser ( String channel , String nick ) { channel = channel . toLowerCase ( ) ; User user = new User ( "" , nick ) ; synchronized ( _channels ) { Hashtable < User , User > users = _channels . get ( channel ) ; if ( users != null ) { return users . remove ( user ) ; } } return null ; }
remove a user from the specified channel in our memory .
