javaFx layoutBounds initialize issue - javafx

Question

in Controller implement Initializable the initialize method I want get box LayoutBounds,but why layoutBounds all property is zero?
package com.erayt.studio.process.component.aggregate.controller;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.layout.VBox;
import java.net.URL;
import java.util.ResourceBundle;
public class TestController implements Initializable {
#FXML
private VBox box;
#Override
public void initialize(URL url, ResourceBundle resourceBundle) {
System.out.println(box.getLayoutBounds());
}
}
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Tab?>
<?import javafx.scene.control.TabPane?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.layout.VBox?>
<VBox fx:id="box" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" xmlns="http://javafx.com/javafx/16" xmlns:fx="http://javafx.com/fxml/1" fx:controller="com.erayt.studio.process.component.aggregate.controller.TestController">
<children>
<TabPane prefHeight="200.0" prefWidth="200.0" tabClosingPolicy="UNAVAILABLE">
<tabs>
<Tab text="Untitled Tab 1">
<content>
<AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" />
</content>
</Tab>
<Tab text="Untitled Tab 2">
<content>
<AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" />
</content>
</Tab>
</tabs>
</TabPane>
</children>
</VBox>