StackedAreaChart appears to be broken when using a CategoryAxis (works fine with Number/Number).

The following code should reproduce - works correctly with a StackedBarChart - however gets a ClassCastException on the StackedAreaChart.

Exception:
Caused by: java.lang.ClassCastException: java.lang.Double cannot be cast to java.lang.String
at javafx.scene.chart.CategoryAxis.getDisplayPosition(CategoryAxis.java:60)
at javafx.scene.chart.StackedAreaChart.layoutPlotChildren(StackedAreaChart.java:431)
at javafx.scene.chart.XYChart.layoutChartChildren(XYChart.java:687)
at javafx.scene.chart.Chart$1.layoutChildren(Chart.java:81)
at javafx.scene.Parent.layout(Parent.java:1018)

Example:


import java.util.Arrays;

import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.chart.CategoryAxis;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.StackedAreaChart;
import javafx.scene.chart.StackedBarChart;
import javafx.scene.chart.XYChart;
import javafx.stage.Stage;

public class TestChart extends Application {
public static void main(String[] args) {
        launch(args);
    }
     
    @Override
    public void start(Stage primaryStage) {
        CategoryAxis xAxis = new CategoryAxis(FXCollections.observableArrayList(Arrays.asList("Jan", "Feb", "Mar", "Apr")));
        xAxis.setLabel("Month");

        NumberAxis yAxis = new NumberAxis();
        yAxis.setLabel("Value");
        
        XYChart<String,Number> stackedChart = new StackedAreaChart<>(xAxis,yAxis);
// XYChart<String,Number> stackedChart = new StackedBarChart<>(xAxis,yAxis);

        XYChart.Series<String,Number> series1 = new XYChart.Series<String,Number>();
        series1.setName("Series 1");
        series1.getData().add(new XYChart.Data<String,Number>("Jan", 100));
        series1.getData().add(new XYChart.Data<String,Number>("Feb", 200));
        series1.getData().add(new XYChart.Data<String,Number>("Mar", 50));
        series1.getData().add(new XYChart.Data<String,Number>("Apr", 75));
 
        XYChart.Series<String,Number> series2 = new XYChart.Series<String,Number>();
        series2.setName("Series 2");
        series2.getData().add(new XYChart.Data<String,Number>("Jan", 50));
        series2.getData().add(new XYChart.Data<String,Number>("Feb", 200));
        series2.getData().add(new XYChart.Data<String,Number>("Mar", 260));
        series2.getData().add(new XYChart.Data<String,Number>("Apr", 100));

        stackedChart.getData().add(series1);
        stackedChart.getData().add(series2);
              
        Group root = new Group();
        root.getChildren().addAll(stackedChart);
        primaryStage.setScene(new Scene(root, 500, 400));
        primaryStage.show();
    }
}