http://aoe-tk.hatenablog.com/entry/2015/07/12/173402 内のサンプルの全コード。

Controller.java

package sample;

import javafx.beans.binding.IntegerBinding;
import javafx.beans.property.IntegerProperty;
import javafx.beans.property.SimpleIntegerProperty;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Label;
import javafx.scene.control.Spinner;
import javafx.scene.control.SpinnerValueFactory;

import java.net.URL;
import java.util.ResourceBundle;

public class Controller implements Initializable {

    @FXML
    Label answer;

    @FXML
    Spinner<Integer> valueA;

    @FXML
    Spinner<Integer> valueB;

    @Override
    public void initialize(URL location, ResourceBundle resources) {
        SpinnerValueFactory.IntegerSpinnerValueFactory vfA =
                new SpinnerValueFactory.IntegerSpinnerValueFactory(0, 100, 1);
        valueA.setValueFactory(vfA);
        SpinnerValueFactory.IntegerSpinnerValueFactory vfB =
                new SpinnerValueFactory.IntegerSpinnerValueFactory(0, 100, 2);
        valueB.setValueFactory(vfB);
        bind();
    }

    private void bind() {
        IntegerProperty a = new SimpleIntegerProperty(0);
        a.bind(valueA.valueProperty());
        IntegerBinding a1 = a.add(1); // a1 = a + 1
        IntegerProperty b = new SimpleIntegerProperty(0);
        b.bind(valueB.valueProperty());
        IntegerBinding b1 = b.add(-1).multiply(2); // b1 = (b - 1) * 2
        answer.textProperty().bind(a1.add(b1).asString()); // a1 + b1
    }

}

ReactiveSampleApp.java

package sample;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class ReactiveSampleApp extends Application {

    @Override
    public void start(Stage primaryStage) throws Exception{
        Parent root = FXMLLoader.load(getClass().getResource("sample.fxml"));
        primaryStage.setTitle("Reactive Sample");
        primaryStage.setScene(new Scene(root));
        primaryStage.show();
    }


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

sample.fxml

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

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

<Pane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="119.0" prefWidth="424.0" xmlns="http://javafx.com/javafx/8.0.40" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Controller">
   <children>
      <Spinner fx:id="valueA" layoutX="39.0" layoutY="43.0" prefHeight="26.0" prefWidth="82.0" />
      <Spinner fx:id="valueB" layoutX="178.0" layoutY="43.0" prefHeight="26.0" prefWidth="82.0" />
      <Label layoutX="127.0" layoutY="48.0" text="+ 1) + (" />
      <Label layoutX="25.0" layoutY="48.0" text="(" />
      <Label layoutX="270.0" layoutY="48.0" text="- 1) * 2 =" />
      <Label fx:id="answer" layoutX="330.0" layoutY="48.0" />
   </children>
</Pane>