Stackoverflow Question https://stackoverflow.com/q/77821399/2423906

test.fxml

<?import javafx.geometry.Insets?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.layout.ColumnConstraints?>
<?import javafx.scene.layout.GridPane?>
<?import javafx.scene.layout.RowConstraints?>
<?import javafx.scene.layout.StackPane?>
<?import javafx.scene.layout.VBox?>
<?import javafx.scene.text.Font?>

<StackPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/18" xmlns:fx="http://javafx.com/fxml/1" fx:controller="com.example.calculator.MainController">
   <children>
      <VBox maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0">
         <children>
            <Label alignment="CENTER_RIGHT" contentDisplay="RIGHT" maxWidth="1.7976931348623157E308" style="-fx-background-color: grey;" text="1,000">
               <VBox.margin>
                  <Insets />
               </VBox.margin>
               <font>
                  <Font size="28.0" />
               </font>
            </Label>
            <StackPane prefHeight="150.0" prefWidth="200.0">
               <children>
                  <GridPane hgap="10.0" maxHeight="-Infinity" maxWidth="-Infinity" vgap="10.0">
                     <columnConstraints>
                        <ColumnConstraints hgrow="SOMETIMES" minWidth="25.0" prefWidth="75.0" />
                        <ColumnConstraints hgrow="SOMETIMES" minWidth="25.0" prefWidth="75.0" />
                        <ColumnConstraints hgrow="SOMETIMES" minWidth="25.0" prefWidth="75.0" />
                        <ColumnConstraints hgrow="SOMETIMES" minWidth="25.0" prefWidth="75.0" />
                     </columnConstraints>
                     <rowConstraints>
                        <RowConstraints minHeight="50.0" prefHeight="30.0" vgrow="SOMETIMES" />
                        <RowConstraints minHeight="50.0" prefHeight="30.0" vgrow="SOMETIMES" />
                        <RowConstraints minHeight="50.0" prefHeight="30.0" vgrow="SOMETIMES" />
                        <RowConstraints minHeight="50.0" prefHeight="30.0" vgrow="SOMETIMES" />
                        <RowConstraints minHeight="50.0" prefHeight="30.0" vgrow="SOMETIMES" />
                     </rowConstraints>
                     <children>
                        <Button maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" mnemonicParsing="false" text="7" />
                        <Button maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" mnemonicParsing="false" text="8" GridPane.columnIndex="1" />
                        <Button maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" mnemonicParsing="false" text="9" GridPane.columnIndex="2" />
                        <Button maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" mnemonicParsing="false" text="/" GridPane.columnIndex="3" />
                        <Button maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" mnemonicParsing="false" text="4" GridPane.rowIndex="1" />
                        <Button maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" mnemonicParsing="false" text="5" GridPane.columnIndex="1" GridPane.rowIndex="1" />
                        <Button maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" mnemonicParsing="false" text="6" GridPane.columnIndex="2" GridPane.rowIndex="1" />
                        <Button maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" mnemonicParsing="false" text="*" GridPane.columnIndex="3" GridPane.rowIndex="1" />
                        <Button maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" mnemonicParsing="false" text="1" GridPane.rowIndex="2" />
                        <Button maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" mnemonicParsing="false" text="2" GridPane.columnIndex="1" GridPane.rowIndex="2" />
                        <Button maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" mnemonicParsing="false" text="3" GridPane.columnIndex="2" GridPane.rowIndex="2" />
                        <Button maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" mnemonicParsing="false" text="-" GridPane.columnIndex="3" GridPane.rowIndex="2" />
                        <Button maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" mnemonicParsing="false" text="0" GridPane.columnSpan="2" GridPane.rowIndex="3" />
                        <Button maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" mnemonicParsing="false" text="=" GridPane.columnIndex="2" GridPane.rowIndex="3" />
                        <Button maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" mnemonicParsing="false" text="+" GridPane.columnIndex="3" GridPane.rowIndex="3" />
                        <Button maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" mnemonicParsing="false" text="C" GridPane.columnIndex="1" GridPane.rowIndex="4">
                           <GridPane.margin>
                              <Insets />
                           </GridPane.margin>
                        </Button>
                        <Button maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" mnemonicParsing="false" text="Mod" GridPane.columnIndex="2" GridPane.rowIndex="4">
                           <GridPane.margin>
                              <Insets />
                           </GridPane.margin>
                        </Button>
                     </children>
                     <padding>
                        <Insets top="20.0" />
                     </padding>
                  </GridPane>
               </children>
            </StackPane>
         </children>
         <StackPane.margin>
            <Insets />
         </StackPane.margin>
         <padding>
            <Insets left="100.0" right="100.0" top="20.0" />
         </padding>
      </VBox>
   </children>
</StackPane>