How to do something when opening a window in JavaFX FXML?

Question

Java

Hello, I started to understand JavaFX and FXML)
There was such a question, how in JavaFX + FXML to launch some kind of action immediately after the application starts?
Those. without any buttons, etc., I just want the for loop to create 10 rectangls immediately after the application starts, but I don’t understand how, because I only know how to do it by clicking on the button)
I have an empty template with a fxml file, a controller and an App class..

<BorderPane xmlns="http://javafx.com/javafx"
            xmlns:fx="http://javafx.com/fxml"
            fx:controller="org.javilingys.MiniPlayerController"
            prefHeight="400.0" prefWidth="600.0"
            stylesheets="css/stylesheet.css">
</BorderPane>

Answer 1

In the case of FXML, you still cannot access fxml elements from the controller constructor, but there is an initialize () method that works after the entire fxml has been initialized, use it.