Notificação Firebase

private DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference();
    private DatabaseReference coordenadasReferencia;

coordenadasReferencia = databaseReference.child("locais");
        coordenadasReferencia.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot s) {

                notify();

                lat = s.child("lat").getValue(String.class);
                longi = s.child("longi").getValue(String.class);
                dados = s.child("dados").getValue(String.class);

                // Pega as duas variáveis
                // e cria o marker
                lat2 = Double.parseDouble(lat);
                longi2 = Double.parseDouble(longi);

                LatLng position2 = new LatLng(lat2, longi2);
                mMap.addMarker(new MarkerOptions()
                        .position(position2)
                        .title(dados.toString()));
                        //.title("vem do fireBase"));
                mMap.moveCamera(CameraUpdateFactory.newLatLng(position2));

                tv1.setText(dados);


            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });

public void notify(View view) {

        Notification.Builder builder = new Notification.Builder(this);
        builder.setContentTitle("Notificação");
        builder.setContentText("Você recebeu uma notificação");
        builder.setSmallIcon(android.R.drawable.sym_action_chat);

        Intent intent = new Intent(this, MapsActivity.class);
        PendingIntent pi = PendingIntent.getActivity(this, 0, intent, 0);
        builder.setContentIntent(pi);
        builder.setAutoCancel(true);

        Notification n = builder.build();

        NotificationManager nm = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
        nm.notify(100, n);
    }