Question

How can I subscribe to a given JFreeChart object to be notified about changes to the series set i.e. a new series inserted or a new data point added to the series?

Answer 1

For a Dataset:

Dataset coll = new XYSeriesCollection();
coll.addChangeListener(new DatasetChangeListener() {
    @Override
    public void datasetChanged(DatasetChangeEvent arg0) {
        // TODO Auto-generated method stub
    }
});

or for the JFreeChart itself:

JFreeChart chart = createChart();
chart.addChangeListener(new ChartChangeListener() {
    @Override
    public void chartChanged(ChartChangeEvent arg0) {
        // TODO Auto-generated method stub
    }
});

And I am sure, that also works for the Plots in between and the Series at the end.

EDIT: To only listen for added/removed series:

final XYSeriesCollection coll = new XYSeriesCollection();
coll.addChangeListener(new DatasetChangeListener() {
    private int numberOfSeries = -1;

    @Override
    public void datasetChanged(DatasetChangeEvent arg0) {
        int numberOfSeriesNew = coll.getSeriesCount();
        if (numberOfSeriesNew == numberOfSeries) {
            // no series was added/removed
        } else if (numberOfSeriesNew < numberOfSeries) {
            // series was removed
            numberOfSeries = numberOfSeriesNew;
        } else {
            // series was added
            numberOfSeries = numberOfSeriesNew;
        }
    }
});