How can I wait a function to finish in Java?

I'm developing an Android app in Java that needs to load some data from a remote database. For that I have a function called getCards() that reads the DB and loads some information into SharedPreferences. In my main function I want to read those infromation written in the SharedPreferencesand write them on a TextView. The thing is that when I try to get those information from SharedPreferencesthey seem to be null because the thread does not wait for "getCards()" to finish. If i go into another activity and then come back in the main activity, the data will be put, but when I first start the activity the read from SharedPreferencesis too fast. Any suggestions? I've tried with wait(100) surrounded by try/catch, but the wapp would crash.

This is the code from the main activity.

        getCards();
       
        ccnr = pref.getString("ccnumber",null);
        ccfn = pref.getString("fullname",null);
        if(ccfn == null || ccnr ==null){
            tvccnumber.setText("No card was added!");
            tvccfullname.setText("No card was added!");

        }else{
            tvccnumber.setText(ccnr);
            tvccfullname.setText(ccfn);
        }

This is the part of getCards() that loads the information in SharedPreferences.

public void getCards(){
        StringRequest stringRequest = new StringRequest(Request.Method.POST, Constants.GETC_URL,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        if(!response.contains("Error!")){
                            JSONArray jsonArray;
                            JSONObject jsonObject;
                            String ccnumber;
                            String fullname;
                            String ccsignature;
                            try {
                                jsonArray = new JSONArray(response);
                                jsonObject = jsonArray.getJSONObject(0);
                                ccnumber = jsonObject.getString("ccNumber");
                                ccsignature = jsonObject.getString("ccSign");
                                fullname = jsonObject.getString("fullName");
                                editor.putString("ccnumber",ccnumber);
                                editor.putString("ccsignature",ccsignature);
                                editor.putString("fullname",fullname);
                                editor.commit();
                            } catch (JSONException e) {
                                e.printStackTrace();
                            }
                        }else{
                            Toast.makeText(FinalUserSpace.this, response, Toast.LENGTH_SHORT).show();
                        }
                    }
                }, new Response.ErrorListener() {
            

You may use a java object to lock until the fonction return.

private Object lock = new Object();

public void getcards(){
        StringRequest stringRequest = new StringRequest(Request.Method.POST, Constants.GETC_URL,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        if(!response.contains("Error!")){
                            JSONArray jsonArray;
                            JSONObject jsonObject;
                            String ccnumber;
                            String fullname;
                            String ccsignature;
                            try {
                                jsonArray = new JSONArray(response);
                                jsonObject = jsonArray.getJSONObject(0);
                                ccnumber = jsonObject.getString("ccNumber");
                                ccsignature = jsonObject.getString("ccSign");
                                fullname = jsonObject.getString("fullName");
                                editor.putString("ccnumber",ccnumber);
                                editor.putString("ccsignature",ccsignature);
                                editor.putString("fullname",fullname);
                                editor.commit();
                            } catch (JSONException e) {
                                e.printStackTrace();
                            }
                        }else{
                            Toast.makeText(FinalUserSpace.this, response, Toast.LENGTH_SHORT).show();
                        }

                        lock.notifyAll();
                    }
                }, new Response.ErrorListener() {

getcards();
       
lock.wait();

ccnr = pref.getString("ccnumber",null);
ccfn = pref.getString("fullname",null);
if(ccfn == null || ccnr ==null){
    tvccnumber.setText("No card was added!");
    tvccfullname.setText("No card was added!");
}else{
    tvccnumber.setText(ccnr);
    tvccfullname.setText(ccfn);
}