Help Line Chat bot

//I'm making a chat bot for LINE (it's a social media) and in my source code lies a problem
//There are a lot of functions, so I will just mention the associated ones.
//TOP OF MY CLASS
    private String profileName = "";

    @Autowired
    private LineMessagingClient lineMessagingClient; //@Autowired and LineMessagingClient are from LINE libraries

    ... //Many functions

    //This function will be called automatically when a user sends a message to my bot
    private void handleTextContent(String replyToken, Event event, TextMessageContent content) {
        String text = content.getText();
        String userId = event.getSource().getUserId();

        //I want my bot to reply the profile name of the user when their message meets certain keywords
        //This is one of the keyword criterias
        if (text.equals("Hi!")) {
            updateProfileName(replyToken, userId); //So I get the profile name first
            String reply = profileName + ",hi!";
            this.reply(replyToken, new TextMessage(reply)); //And then I tell the bot to reply
        }
    }

    private void updateProfileName(String replyToken, String userId) throws Exception {
        profileName = "Unknown"; //Sometimes userId can be null if the user doesn't agree to LINE Terms, so firstly I set it to Unknown
        //I copied the * part from internet, so I don't really know how it works
        //I also don't really understand how synchronized works
        synchronized (lineMessagingClient) {
            try {
                if (userId != null) {
                    //Start * part
                    lineMessagingClient
                        .getProfile(userId)
                        .whenComplete((profile, throwable) -> {
                            //What I know with this lambda is that it is slow in getting the username
                            //So I use the wait & notify I found on the internet to make
                            //this function finished after the username has been gained successfully
                            if (throwable != null) {
                                this.reply(replyToken, new TextMessage(throwable.getMessage()));
                                return;
                            }
                            profileName = profile.getDisplayName();
                            lineMessagingClient.notifyAll(); //The & part
                        });
                    //End * part
                     lineMessagingClient.wait(); //The ^ part
                }
            } catch (Exception e) {
                System.out.println("EXCEPTION!");
            }
        }
    }

    //Now the problem is that the & part fails to stop the ^ part
    //In other words when I send "Hi!" to my bot there is no further response
    //Before I added wait & notify my bot responded, but it responded "Unknown, hi!" instead of my name and hi
    //I'm sure I misunderstood how wait & notify works, I researched in the internet but didn't really understand
    //Is there any way to fix this so that my bot works as how I want?