Selecting from Firebase Realtime Database

Question

public static User getUser(String userFirebaseID){
    Log.d("Activitati","<<<< IN FirebaseRealtimeDBUtils.getUser() >>>> ");
    Log.d("Activitati","userFirebaseID: "+userFirebaseID);
    final User[] user = new User[1];
    // Get a reference to our posts
    final FirebaseDatabase database = FirebaseDatabase.getInstance();
    DatabaseReference ref = database.getReference("USERS");
    ref.child(userFirebaseID).addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            //for(DataSnapshot child: dataSnapshot.getChildren()){
            Log.d("Activitati","dataSnapshot: "+dataSnapshot.toString());
                user[0] = dataSnapshot.getValue(User.class);
                doSomethingWithUser(user[0]);
                Log.d("Activitati",getClass().getName()+" User object: "+ user[0]);
                Log.d("Activitati",getClass().getName()+" User email address from DB: "+ user[0].getEmailAddress());
            //}
        }
        @Override
        public void onCancelled(DatabaseError databaseError) {
            Log.d("Activitati",getClass().getName()+" DB ERROR: "+databaseError.getMessage());
        }

    });
    Log.d("Activitati","<<<< OUT FirebaseRealtimeDBUtils.getUser() >>>> ");
    return user[0];
}

public static void doSomethingWithUser(User user){
    Log.d("Activitati"," User email address from DB: "+ user.getEmailAddress());
}

It keeps giving me

Process: ro.LearnByPlaying.Activitati, PID: 16319
  java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String ro.LearnByPLaying.Beans.User.getEmailAddress()' on a null object reference
      at ro.LearnByPLaying.Activitati.LoginActivity$1$2.onComplete(LoginActivity.java:104)
      at com.google.android.gms.tasks.zzj.run(Unknown Source:23)
      at android.os.Handler.handleCallback(Handler.java:790)
      at android.os.Handler.dispatchMessage(Handler.java:99)
      at android.os.Looper.loop(Looper.java:164)
      at android.app.ActivityThread.main(ActivityThread.java:6494)
      at java.lang.reflect.Method.invoke(Native Method)
      at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)

And my database has this structure:
My DB structure:

But I don't get the user , can someone tell me if I did the select wrong ?

The USER class I have created, I didn't include the get and set for each propertie to not make a wall of text:

public class User implements Serializable{
private String firstName;
private String lastName;
private String nickName;
private Date dateOfBirth;
private String country;
private String town;
private String phoneNumber;
private String phoneModel;
private String emailAddress;
private String userFirebaseID;
private String dateAccountCreated;
... (getters and setters are generated too )

and I call my main method for getting the user like this:

User userObject = FirebaseRealtimeDBUtils.getUser(USER_FIREBASE_ID);

where

USER_FIREBASE_ID is auth.getUid();

Answer 1

SOLUTION(TEMPORARY):
First I want to thank you again Levi Albuquerque , i resolved my problem by doing this: - I am not using a method ,I am doing the select directly in the class that I need the response(object User) (THE SAME SELECT) - and this is what I got:

final User[] user = new User[1];
final FirebaseDatabase database = FirebaseDatabase.getInstance();
                                    DatabaseReference ref = database.getReference("USERS");
                                    ref.child(USER_FIREBASE_ID).addValueEventListener(new ValueEventListener() {
                                                                                          @Override
                                                                                          public void onDataChange(DataSnapshot dataSnapshot) {
                                                                                              user[0] = dataSnapshot.getValue(User.class);
                                                                                              Log.d("Activitati", "child email: ---------- " + user[0].getEmailAddress());
                                                                                              intent.putExtra("SESSION_USER", user[0]);
                                                                                              startActivity(intent);
                                                                                              finish();
                                                                                          }

                                                                                          @Override
                                                                                          public void onCancelled(DatabaseError databaseError) {
                                                                                              Log.d("Activitati", getClass().getName() + " DB ERROR: " + databaseError.getMessage());
                                                                                          }
                                                                                      });

I did this for 2 reasons:
intent.putExtra("SESSION_USER", user[0]);
startActivity(intent);
finish();

1) My log was showing me that it started the activity and weirdly the select form DB was done after the activity started not before

2) The select was done i got the user object but it didn't have time to put it in session(intent) cause i never got it in the second activity so my solutions was just to start the activity after the last line of code when getting the user from FirebaseDB