android foreground push notification

1// When app is in foreground, notifications are not generated themselves. You need to write some additional code. When message is received onMessageReceived() method is called where you can generate the notification. Here is the code:
2
3public class MyFirebaseMessagingService extends FirebaseMessagingService {
4    @Override
5    public void onMessageReceived(RemoteMessage remoteMessage) {
6        super.onMessageReceived(remoteMessage);
7        Log.d("msg", "onMessageReceived: " + remoteMessage.getData().get("message"));
8        Intent intent = new Intent(this, MainActivity.class);
9        intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
10        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_ONE_SHOT);
11        String channelId = "Default";
12        NotificationCompat.Builder builder = new  NotificationCompat.Builder(this, channelId)
13                .setSmallIcon(R.mipmap.ic_launcher)
14                .setContentTitle(remoteMessage.getNotification().getTitle())
15                .setContentText(remoteMessage.getNotification().getBody()).setAutoCancel(true).setContentIntent(pendingIntent);;
16        NotificationManager manager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
17        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
18            NotificationChannel channel = new NotificationChannel(channelId, "Default channel", NotificationManager.IMPORTANCE_DEFAULT);
19            manager.createNotificationChannel(channel);
20        }
21        manager.notify(0, builder.build());
22    }
23}