Calculator written in Java 8 with JavaFX 8 + SceneBuilder 2.0

App.java

package net.argius.calculator;

import java.math.BigDecimal;
import javafx.application.Application;
import javafx.application.Platform;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextField;
import javafx.stage.Stage;

public final class App extends Application {

    private BigDecimal left;
    private String selectedOperator;
    private boolean numberInputting;

    @FXML
    private TextField display;

    public App() {
        this.left = BigDecimal.ZERO;
        this.selectedOperator = "";
        this.numberInputting = false;
    }

    @Override
    public void start(Stage stage) throws Exception {
        stage.setTitle("Calculator");
        stage.setOnCloseRequest(x -> {
            Platform.exit();
        });
        stage.setResizable(false);
        stage.setScene(new Scene(FXMLLoader.load(getClass().getResource("main.fxml"))));
        stage.show();
    }

    @FXML
    protected void handleOnAnyButtonClicked(ActionEvent evt) {
        Button button = (Button)evt.getSource();
        final String buttonText = button.getText();
        if (buttonText.equals("C") || buttonText.equals("AC")) {
            if (buttonText.equals("AC")) {
                left = BigDecimal.ZERO;
            }
            selectedOperator = "";
            numberInputting = false;
            display.setText("0");;
            return;
        }
        if (buttonText.matches("[0-9\\.]")) {
            if (!numberInputting) {
                numberInputting = true;
                display.clear();
            }
            display.appendText(buttonText);
            return;
        }
        if (buttonText.matches("[＋－×÷]")) {
            left = new BigDecimal(display.getText());
            selectedOperator = buttonText;
            numberInputting = false;
            return;
        }
        if (buttonText.equals("=")) {
            final BigDecimal right = numberInputting ? new BigDecimal(display.getText()) : left;
            left = calculate(selectedOperator, left, right);
            display.setText(left.toString());
            numberInputting = false;
            return;
        }
    }

    static BigDecimal calculate(String operator, BigDecimal left, BigDecimal right) {
        switch (operator) {
            case "＋":
                return left.add(right);
            case "－":
                return left.subtract(right);
            case "×":
                return left.multiply(right);
            case "÷":
                return left.divide(right);
            default:
        }
        return right;
    }

    public static void main(String[] args) {
        launch(args);
    }

}

main.css

.background {
  -fx-background-color: #663333;
}
.button {
  -fx-background-color: silver;
}
.display {
  -fx-background-color: #cccccc;
}

main.fxml

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.text.*?>
<?import javafx.geometry.*?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>

<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="249.0" prefWidth="244.0" styleClass="background" stylesheets="@main.css" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="net.argius.calculator.App">
   <children>
      <Button layoutX="71.0" layoutY="171.0" mnemonicParsing="false" onAction="#handleOnAnyButtonClicked" text="1" />
      <Button layoutX="106.0" layoutY="171.0" mnemonicParsing="false" onAction="#handleOnAnyButtonClicked" text="2" />
      <Button layoutX="140.0" layoutY="171.0" mnemonicParsing="false" onAction="#handleOnAnyButtonClicked" text="3" />
      <Button layoutX="71.0" layoutY="134.0" mnemonicParsing="false" onAction="#handleOnAnyButtonClicked" text="4" />
      <Button layoutX="106.0" layoutY="134.0" mnemonicParsing="false" onAction="#handleOnAnyButtonClicked" text="5" />
      <Button layoutX="140.0" layoutY="134.0" mnemonicParsing="false" onAction="#handleOnAnyButtonClicked" text="6" />
      <Button layoutX="71.0" layoutY="97.0" mnemonicParsing="false" onAction="#handleOnAnyButtonClicked" text="7" />
      <Button layoutX="106.0" layoutY="97.0" mnemonicParsing="false" onAction="#handleOnAnyButtonClicked" text="8" />
      <Button layoutX="140.0" layoutY="97.0" mnemonicParsing="false" onAction="#handleOnAnyButtonClicked" text="9" />
      <TextField fx:id="display" alignment="BOTTOM_RIGHT" editable="false" layoutX="31.0" layoutY="14.0" prefHeight="35.0" prefWidth="178.0" styleClass="display" text="0">
         <font>
            <Font name="Lucida Console" size="20.0" />
         </font>
      </TextField>
      <Button layoutX="27.0" layoutY="97.0" mnemonicParsing="false" onAction="#handleOnAnyButtonClicked" text="C" />
      <Button layoutX="167.0" layoutY="208.0" mnemonicParsing="false" onAction="#handleOnAnyButtonClicked" prefHeight="23.0" prefWidth="47.0" text="=" />
      <Button layoutX="187.0" layoutY="171.0" mnemonicParsing="false" onAction="#handleOnAnyButtonClicked" text="＋" />
      <Button layoutX="71.0" layoutY="208.0" mnemonicParsing="false" onAction="#handleOnAnyButtonClicked" text="0" />
      <Button layoutX="187.0" layoutY="134.0" mnemonicParsing="false" onAction="#handleOnAnyButtonClicked" text="－" />
      <Button layoutX="188.0" layoutY="97.0" mnemonicParsing="false" onAction="#handleOnAnyButtonClicked" prefHeight="23.0" prefWidth="25.0" styleClass="background" text="×" />
      <Button layoutX="188.0" layoutY="61.0" mnemonicParsing="false" onAction="#handleOnAnyButtonClicked" styleClass="background" text="÷" />
      <Button layoutX="25.0" layoutY="61.0" mnemonicParsing="false" onAction="#handleOnAnyButtonClicked" text="AC" />
      <Button layoutX="142.0" layoutY="208.0" mnemonicParsing="false" onAction="#handleOnAnyButtonClicked" text="." />
   </children>
</AnchorPane>

Thank you!
Great code!