Java Fx Category Axis out of order

Question

I have a chart where I REPLACE the data in a XY chart with new String,Number pairs and I get the category axis labels out of order. They retain part of the order of the previous chart that has had its data deleted.
Here is a demo app that shows the behavior. Just click on the chart a couple of times while looking at the x axis. The first time the data is plotted all is ok, after other data is plotted, the category axis gets screwed up for the original data.
Any help?????
Tom
package testCategoryBug;
import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.event.EventHandler;
import javafx.scene.chart.CategoryAxis;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.XYChart;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.chart.LineChart;
import javafx.scene.chart.XYChart.Data;
import javafx.scene.chart.XYChart.Series;
import javafx.scene.input.MouseEvent;
public class TestCategoryBug extends Application {
      static Boolean even=true;
    @Override public void start(Stage stage) {
        stage.setTitle("Test Category Bug");   
        final CategoryAxis xAxis = new CategoryAxis();
        final NumberAxis yAxis = new NumberAxis();
        xAxis.setLabel("Month");      
        final LineChart<String,Number> lineChart = new LineChart<String,Number>(xAxis, yAxis);      
        lineChart.setTitle("Stock Monitoring, 2010");    
        // Initialize some data for plotting.
         final Series<String, Number> plottablePairs  = new Series<String, Number>();
         final Series<String, Number> plottablePairs2 = new Series<String, Number>();
        for (int i = 0; i < 10; i++) {
            Data<String,Number> pair= new Data<String,Number>("Month "+i,10.0*i);
            plottablePairs.getData().add(pair);
        for (int i = 5; i < 10; i++) {
            Data<String,Number> pair= new Data<String,Number>("Month "+i,100.0-10*i);
            plottablePairs2.getData().add(pair);
        // add the first of the series
          final ObservableList<XYChart.Series<String, Number>> chartData=FXCollections.observableArrayList();;
          chartData.add(plottablePairs);
          lineChart.setData(chartData);
          // now on a mouse click, swap the data.  Click twice and see what happens
          lineChart.addEventHandler(MouseEvent.MOUSE_CLICKED,new EventHandler<MouseEvent>() {
            @Override
            public void handle(MouseEvent e) {
                chartData.clear();
                if (even) {
                    chartData.add(plottablePairs2);
                } else {
                    chartData.add(plottablePairs);
                    // note that after this, the axis is screwed up.
                lineChart.setData(chartData);
                even=!even;
          // Put up the scene
          Scene scene  = new Scene(lineChart,800,600);
          stage.setScene(scene);
          stage.show();
    public static void main(String[] args) {
        launch(args);

Answer 1

Obviously you just posted a simple example to demonstrate the problem, so I don't know if this workaround works for your real application, but could you just replace the entire chart?
import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.scene.chart.CategoryAxis;
import javafx.scene.chart.NumberAxis;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.chart.LineChart;
import javafx.scene.chart.XYChart.Data;
import javafx.scene.chart.XYChart.Series;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.BorderPane;
public class TestCategoryBug extends Application {
  private boolean even = true;
  @Override
  public void start(Stage stage) {
    stage.setTitle("Test Category Bug");
    // Initialize some data for plotting.
    final Series<String, Number> plottablePairs = new Series<String, Number>();
    final Series<String, Number> plottablePairs2 = new Series<String, Number>();
    for (int i = 0; i < 10; i++) {
      Data<String, Number> pair = new Data<String, Number>("Month " + i,
          10.0 * i);
      plottablePairs.getData().add(pair);
    for (int i = 5; i < 10; i++) {
      Data<String, Number> pair = new Data<String, Number>("Month " + i,
          100.0 - 10 * i);
      plottablePairs2.getData().add(pair);
    final BorderPane root = new BorderPane();
    displayLineChart(root, plottablePairs, plottablePairs2);
    // now on a mouse click, swap the data. Click twice and see what happens
    root.addEventHandler(MouseEvent.MOUSE_CLICKED,
        new EventHandler<MouseEvent>() {
          @Override
          public void handle(MouseEvent e) {
            even = !even;
            displayLineChart(root, plottablePairs, plottablePairs2);
    // Put up the scene
    final Scene scene = new Scene(root, 800, 600);
    stage.setScene(scene);
    stage.show();
  private void displayLineChart(BorderPane root, Series<String, Number> plottablePairs, Series<String, Number> plottablePairs2) {
   final CategoryAxis xAxis = new CategoryAxis();
    xAxis.setLabel("Month");
    final NumberAxis yAxis = new NumberAxis();
    LineChart<String, Number> lineChart = new LineChart<>(xAxis, yAxis);
    lineChart.setTitle("Stock Monitoring, 2010");
    if (even) {
      lineChart.getData().add(plottablePairs2);
    } else {
      lineChart.getData().add(plottablePairs);
    root.setCenter(lineChart);
  public static void main(String[] args) {
    launch(args);