FS DB reading all documents

 //Getting instance
        FirebaseFirestore db = FirebaseFirestore.getInstance();

        //Getting Reference to "users" collection
        final CollectionReference collectionReference = db.collection("users");

        //Calling the get() method with a callback function
        collectionReference.get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
            public void onComplete(@NonNull Task<QuerySnapshot> task) {
                if (task.isSuccessful()) {
                    //Task is successful
                    //Running enhanced for loop to get each document
                    for (QueryDocumentSnapshot documentSnapshot: task.getResult()){
                        //Printing data of each document to log
                        Log.i(TAG, "onComplete: query data: " + documentSnapshot.getData());
                    //Task was not successful
                    Log.e(TAG, "onComplete: ERROR: " + task.getException().getLocalizedMessage() );