Загрузка данных

<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.geometry.Insets?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.text.Font?>

<VBox alignment="CENTER" spacing="10.0" style="-fx-background-color: #2c3e50;" xmlns="http://javafx.com/javafx/11.0.2" xmlns:fx="http://javafx.com/fxml/1" fx:controller="com.example.demo.HelloController">
    <padding>
        <Insets bottom="20.0" left="20.0" right="20.0" top="20.0" />
    </padding>

    <TextField fx:id="display" editable="false" alignment="CENTER_RIGHT" prefHeight="50.0" style="-fx-background-color: #ecf0f1;">
        <font>
            <Font name="System Bold" size="18.0" />
        </font>
    </TextField>

    <GridPane hgap="10.0" vgap="10.0">
        <Button onAction="#onDigitClick" text="7" prefWidth="50" GridPane.columnIndex="0" GridPane.rowIndex="0" />
        <Button onAction="#onDigitClick" text="8" prefWidth="50" GridPane.columnIndex="1" GridPane.rowIndex="0" />
        <Button onAction="#onDigitClick" text="9" prefWidth="50" GridPane.columnIndex="2" GridPane.rowIndex="0" />
        <Button onAction="#onOperatorClick" text="/" prefWidth="50" GridPane.columnIndex="3" GridPane.rowIndex="0" style="-fx-background-color: #f39c12;" />

        <Button onAction="#onDigitClick" text="4" prefWidth="50" GridPane.columnIndex="0" GridPane.rowIndex="1" />
        <Button onAction="#onDigitClick" text="5" prefWidth="50" GridPane.columnIndex="1" GridPane.rowIndex="1" />
        <Button onAction="#onDigitClick" text="6" prefWidth="50" GridPane.columnIndex="2" GridPane.rowIndex="1" />
        <Button onAction="#onOperatorClick" text="*" prefWidth="50" GridPane.columnIndex="3" GridPane.rowIndex="1" style="-fx-background-color: #f39c12;" />

        <Button onAction="#onDigitClick" text="1" prefWidth="50" GridPane.columnIndex="0" GridPane.rowIndex="2" />
        <Button onAction="#onDigitClick" text="2" prefWidth="50" GridPane.columnIndex="1" GridPane.rowIndex="2" />
        <Button onAction="#onDigitClick" text="3" prefWidth="50" GridPane.columnIndex="2" GridPane.rowIndex="2" />
        <Button onAction="#onOperatorClick" text="-" prefWidth="50" GridPane.columnIndex="3" GridPane.rowIndex="2" style="-fx-background-color: #f39c12;" />

        <Button onAction="#onDigitClick" text="0" prefWidth="50" GridPane.columnIndex="0" GridPane.rowIndex="3" />
        <Button onAction="#onClearClick" text="C" prefWidth="50" GridPane.columnIndex="1" GridPane.rowIndex="3" style="-fx-background-color: #e74c3c;" />
        <Button onAction="#onResultClick" text="=" prefWidth="50" GridPane.columnIndex="2" GridPane.rowIndex="3" style="-fx-background-color: #2ecc71;" />
        <Button onAction="#onOperatorClick" text="+" prefWidth="50" GridPane.columnIndex="3" GridPane.rowIndex="3" style="-fx-background-color: #f39c12;" />
    </GridPane>
</VBox>