XYSeries s2 = new XYSeries("Series 2", true, false);
s2.add(5.0, 5.0);
s2.add(10.0, 15.5);
s2.add(15.0, 9.5);
s2.add(20.0, 3.5);
dataset.addSeries(s2);
XYPlot plot = new XYPlot(dataset,
new NumberAxis("X"), new NumberAxis("Y"),
new XYStepAreaRenderer());
JFreeChart chart = new JFreeChart(plot);
/* BufferedImage image = */ chart.createBufferedImage(300, 200,