Vaadin 8 | Notifications

To show to the user notifications. You can do as follows:

public class DemoUI extends UI {
  DefaultNotificationHolder notifications = new DefaultNotificationHolder();

  @Override
    protected void init(VaadinRequest request) {
       AppLayout drawer = AppLayoutBuilder.get(variant)
                ...
                .addToAppBar(new AppBarNotificationButton(notifications, true);
                ...
                .build();
       setContent(drawer);
   }
}