Service to check if JSON file is updated if updated Notification to user

Question

abc.json

[{"id":1,"title":"1. heading of Tips","description":"welcome to post 1"},{"id":2,"title":"2. heading of Tips","description":"welcome to post 2"},{"id":3,"title":"3. heading of Tips","description":"welcome to post 3"},{"id":4,"title":"4. heading of Tips","description":"welcome to post 4"}]

I am new to android. I want my service to check JSON file on server whether it have been updated. If updated it will copy last element of the array and pass them as notification through sendNotification() method.

MyService.java

public class MyService extends Service {
    private static final String TAG = "MyService";
    String heading="this is heading";
    String post = "this is post";
    public MyService() {
    }

    @Override
    public IBinder onBind(Intent intent) {

        throw new UnsupportedOperationException("Not yet implemented");
    }


    @Override
    public void onCreate() {
        Toast.makeText(this, "The new Service was Created", Toast.LENGTH_SHORT).show();



        // call the on Message received
        onMessageReceived(heading,post);

    }
   public void onMessageReceived(String remoteMessage, String body) {
        // TODO(developer): Handle FCM messages here.
        // If the application is in the foreground handle both data and notification messages here.
        // Also if you intend on generating your own notifications as a result of a received FCM
        // message, here is where that should be initiated. See sendNotification method below.
        Log.d(TAG, "From: " + remoteMessage);
        Log.d(TAG, "Notification Message Body: " + body);
       sendNotification(remoteMessage,body);
    }
    // [END receive_message]
    /**
     * Create and show a simple notification containing the received FCM message.
     *
     * @param messageBody FCM message body received.
     */
    private void sendNotification(String messageBody, String post) {
        Intent intent = new Intent(this, MainActivity.class);
        intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0 /* Request code */, intent,
                PendingIntent.FLAG_ONE_SHOT);

        Uri defaultSoundUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
        NotificationCompat.Builder notificationBuilder = (NotificationCompat.Builder) new NotificationCompat.Builder(this)
                .setSmallIcon(R.drawable.ic_icon)
                .setContentTitle(post)
                .setContentText(messageBody)
                .setAutoCancel(true)
                .setSound(defaultSoundUri)
                .setContentIntent(pendingIntent);

        NotificationManager notificationManager =
                (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

        notificationManager.notify(0 /* ID of notification */, notificationBuilder.build());
    }

    // send notification ends


    @Override
    public void onDestroy() {
        Toast.makeText(this, "Service Destroyed", Toast.LENGTH_LONG).show();

    }

}