public class UserImpl extends User {
  public UserImpl(ChatMediator med, String name) {
  super(med, name);
  }
  @Override
  public void send(String msg){
  System.out.println(this.name+": Sending Message="+msg);
  mediator.sendMessage(msg, this);
  }

  @Override
  public void receive(String msg) {
  System.out.println(this.name+": Received Message:"+msg);
  }
}