FireStore v2

private void ReadSingleContact() {
        DocumentReference user = db.collection("PhoneBook").document("Contacts");
        user.get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
            @Override
            public void onComplete(@NonNull Task<DocumentSnapshot> task) {
                if (task.isSuccessful()){
                    DocumentSnapshot doc = task.getResult();
                    StringBuilder fields = new StringBuilder("");
                    fields.append("Name: ").append(doc.get("Name"));
                    fields.append("\nEmail: ").append(doc.get("Email"));
                    fields.append("\nPhone: ").append(doc.get("Phone"));
                    textDisplay.setText(fields.toString());
                }
            }
        })
                .addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                    }
                });
    }