How to Safely Update JFreeChart Series from a Background Thread?

Unexpected Errors While Modifying Series with JFreeChart

Problem:
In an attempt to dynamically update a JFreeChart plot, a user encountered "Series index out of bounds" and "index out of bounds" exceptions when trying to change the dataset within a background thread.

Root Cause:
The issue was that the dataset was being modified directly from a background thread, which is not a thread-safe operation.

Resolution:
To ensure thread-safe updates, the user should utilize a SwingWorker. This class provides a safe way to update the GUI from background threads by updating the dataset in the process() method, which is invoked on the Event Dispatch Thread (EDT).

Alternative Solution:
For situations where the X-axis represents a count or number of iterations rather than time, NumberAxis should be used instead of DateAxis. This change also allows for updates to the plot as computations complete, rather than at fixed time intervals.

Example Code Implementation:

private XYSeries series = new XYSeries("Result");
...
@Override
protected void process(List<double> chunks) {
    for (double d : chunks) {
        label.setText(df.format(d));
        series.add(++n, d);
    }
}</double>

In this code, the process() method is used to safely update the XYSeries dataset on the EDT as new data becomes available. The XYLineAndShapeRenderer is set to render shapes for the first series, making the points visible on the plot.

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