public static boolean listaContactosExiste(Context context) {
        Firebase ref = new Firebase(context.getString(R.string.firebaseURL));
        final boolean[] existe = new boolean[1];
        ref.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot snapshot) {
                existe[0] = snapshot.hasChild("Contacts");
            }

            @Override
            public void onCancelled(FirebaseError firebaseError) {
            }
        });
        return existe[0];
    }
}