For context, I am making an app which communicates with TCP server hosted currently on my local pc. I am using SSLSocket for secure connection. All communications are ok. I have made a special class for handling all communications with the server. I know that I have to do it on background thread so I have already initialized ExecutorService and Handler in the class. Before explaining the problem, let me show the code of the class and when I call it.

Communication Class :-

private ExecutorService executor = Executors.newSingleThreadExecutor();
private Handler handler = new Handler(Looper.getMainLooper());


    public String genAuthToken(String userName, String passwd) throws Exception{
        if(!connected)return null;
        JSONObject json = new JSONObject();
        json.put("func","genAuthToken");
        json.put("userName",userName);
        json.put("passwd",passwd);
        JSONObject finalJSON = json;
        final String[] reply = {""};
  
        pw.println(finalJSON);
        reply[0] = scan.nextLine();
        
        json = new JSONObject(reply[0]);
        if((int) json.get("code") == 200){
            this.authToken = json.get("authToken").toString();
            return (String) json.get("authToken");
        }
        return String.valueOf((int) json.get("code"));
    }

MainActivity.java :-

LedGo client = new LedGo();
        boolean connected = client.connect("192.168.1.4",1304,cf,()->{},()->{Snackbar.make(view,"Couldn't connect to server",Snackbar.LENGTH_SHORT).setAnchorView(R.id.fab).show();});
        String authToken = client.genAuthToken("userName","passwd",true,()->{},()->{});

Now the problem is that I want to get authToken in MainActivity.java. I know that I cannot get it like I wrote above but I want to know how can I extract some data from ExecutorService. I thought of one option of making a public variable which could be accessed by MainActivity but that is not practical because app would be sending many requests from different thread at same time. In short, I want to know how to get variable from ExecutorService.execute() in MainActivity.java. If anything is not clear please tell me, I would really appreciate the help.

How to get some values from ExecutorService.execute() function in Android Development, Java