private boolean receiveMessage(Message message) {

        if (this.enemies.contains(message.getSender())){
            return false;
        }
        else if (this.friends.contains(message.getSender())) {
            this.wall.add(message);
            return true;
        }
        else if (message.getMessage().equals("/friend")){
                this.friends.add(message.getSender());
                return true;
        }
        else
            return false;
        }