JavaFX line chart don't clear properly

Question

In the example below you can see that, depending on the selected check box, program ploting series aSeries or bSeries . For the first time chart is ploted ok, but when I trying to plot chart again, it receives an exception java.lang.IllegalArgumentException: Duplicate series added. Before plot again I clean previous series.

I checked the solution on this page JavaFX Duplicate Series Added, I turned off the animations but it not help me.

Also check this: JavaFX Chart - Java.lang.IllegalArgumentException : Duplicate series added but i don't exactly know what is the difference i think i'm doing the same.

Example:

public class MainController implements Initializable {

XYChart.Series<String, Number> aSeries = new XYChart.Series<String, Number>();
XYChart.Series<String, Number> bSeries = new XYChart.Series<String, Number>();

@FXML
private LineChart<String, Number> lineChart;

@FXML
private CheckBox aCheckBox, bCheckBox;

@Override
public void initialize(URL location, ResourceBundle resources) {
    lineChart.setAnimated(false);

    aCheckBox.setOnAction(new EventHandler<ActionEvent>() {
        @Override
        public void handle(ActionEvent event) {
            chartConfiguration();
        }
    });

    bCheckBox.setOnAction(new EventHandler<ActionEvent>() {
        @Override
        public void handle(ActionEvent event) {
            chartConfiguration();
        }
    });
}

@SuppressWarnings("unchecked")
private void chartConfiguration() {

    if (!aCheckBox.isSelected() && aSeries.getData().size() > 0) {
        aSeries.getData().clear();

    }
    if (!bCheckBox.isSelected() && bSeries.getData().size() > 0) {
        bSeries.getData().clear();

    }
    if (aCheckBox.isSelected() && aSeries.getData().size() == 0) {

        aSeries.getData().add(new XYChart.Data<String, Number>("Jan", 50.0));
        aSeries.getData().add(new XYChart.Data<String, Number>("Feb", 70.0));
        lineChart.getData().addAll(aSeries);

    }
    if (bCheckBox.isSelected() && bSeries.getData().size() == 0) {

        bSeries.getData().add(new XYChart.Data<String, Number>("Jan", 30.0));
        bSeries.getData().add(new XYChart.Data<String, Number>("Feb", 50.0));
        lineChart.getData().addAll(bSeries);
    }
}
}

My question is why program throws Duplicate series added and how can i fix this?

EDIT:

Like Sedrik suggest I modificate the code but after one plotting when i trying to plot next draw , nothing happened...

Change code below:

}

@SuppressWarnings("unchecked")
private void chartConfiguration() {

    if (!aCheckBox.isSelected() && aSeries.getData().size() > 0) {
        //aSeries.getData().clear();
        lineChart.getData().clear();


    }
    if (!bCheckBox.isSelected() && bSeries.getData().size() > 0) {
        //bSeries.getData().clear();
        lineChart.getData().clear();

    }
    if (aCheckBox.isSelected() && aSeries.getData().size() == 0) {

        aSeries.getData().add(new XYChart.Data<String, Number>("Jan", 50.0));
        aSeries.getData().add(new XYChart.Data<String, Number>("Feb", 70.0));
        lineChart.getData().addAll(aSeries);

    }
    if (bCheckBox.isSelected() && bSeries.getData().size() == 0) {

        bSeries.getData().add(new XYChart.Data<String, Number>("Jan", 30.0));
        bSeries.getData().add(new XYChart.Data<String, Number>("Feb", 50.0));
        lineChart.getData().addAll(bSeries);
    }
}