FULL PRODUCT VERSION :
java version "1.8.0_131"
Java(TM) SE Runtime Environment (build 1.8.0_131-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.131-b11, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]

A DESCRIPTION OF THE PROBLEM :
When using Line chart with more than one data series
the elements values of the first X_AXIS will be first regardless of their location together in the two series

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
please run the example



EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Jan must be the first element in the X_Axis and not June
ACTUAL -
Jun is the first because of the order of the series

        lineChart.getData().addAll(series1, series2, series3);



REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
package app.dlg.form;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.chart.CategoryAxis;
import javafx.scene.chart.LineChart;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.XYChart;
import javafx.stage.Stage;
 
 
public class LineChartSample extends Application {
 
    @Override public void start(Stage stage) {
        stage.setTitle("Line Chart Sample");
        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");
                          
        XYChart.Series series1 = new XYChart.Series();
        series1.setName("Portfolio 1");
        
        XYChart.Series series2 = new XYChart.Series();
        series2.setName("Portfolio 2");
        
        XYChart.Series series3 = new XYChart.Series();
        series3.setName("Portfolio 3");
        
// series1.getData().add(new XYChart.Data("Jan", 23));
// series1.getData().add(new XYChart.Data("Feb", 14));
// series1.getData().add(new XYChart.Data("Mar", 15));
// series1.getData().add(new XYChart.Data("Apr", 24));
// series1.getData().add(new XYChart.Data("May", 34));
        series1.getData().add(new XYChart.Data("Jun", 36));
        series1.getData().add(new XYChart.Data("Jul", 22));
        series1.getData().add(new XYChart.Data("Aug", 45));
        series1.getData().add(new XYChart.Data("Sep", 43));
        series1.getData().add(new XYChart.Data("Oct", 17));
        series1.getData().add(new XYChart.Data("Nov", 29));
        series1.getData().add(new XYChart.Data("Dec", 25));
        
// series2.getData().add(new XYChart.Data("Jan", 33));
// series2.getData().add(new XYChart.Data("Feb", 34));
// series2.getData().add(new XYChart.Data("Mar", 25));
// series2.getData().add(new XYChart.Data("Apr", 44));
// series2.getData().add(new XYChart.Data("May", 39));
// series2.getData().add(new XYChart.Data("Jun", 16));
// series2.getData().add(new XYChart.Data("Jul", 55));
        series2.getData().add(new XYChart.Data("Aug", 54));
        series2.getData().add(new XYChart.Data("Sep", 48));
        series2.getData().add(new XYChart.Data("Oct", 27));
        series2.getData().add(new XYChart.Data("Nov", 37));
        series2.getData().add(new XYChart.Data("Dec", 29));
        
        series3.getData().add(new XYChart.Data("Jan", 44));
        series3.getData().add(new XYChart.Data("Feb", 35));
        series3.getData().add(new XYChart.Data("Mar", 36));
        series3.getData().add(new XYChart.Data("Apr", 33));
        series3.getData().add(new XYChart.Data("May", 31));
        series3.getData().add(new XYChart.Data("Jun", 26));
        series3.getData().add(new XYChart.Data("Jul", 22));
        series3.getData().add(new XYChart.Data("Aug", 25));
        series3.getData().add(new XYChart.Data("Sep", 43));
        series3.getData().add(new XYChart.Data("Oct", 44));
        series3.getData().add(new XYChart.Data("Nov", 45));
        series3.getData().add(new XYChart.Data("Dec", 44));
        
        Scene scene = new Scene(lineChart,800,600);
        lineChart.getData().addAll(series1, series2, series3);
       
        stage.setScene(scene);
        stage.show();
    }
 
 
    public static void main(String[] args) {
        launch(args);
    }
---------- END SOURCE ----------