example:
XYSeries series = new XYSeries("Average Size");
series.add(20.0, 10.0);
series.add(40.0, 20.0);
series.add(70.0, 50.0);
XYDataset xyDataset = new XYSeriesCollection(series);JFreeChart chart = ChartFactory.createAreaXYChart
                     ("Sample XY Chart",  // Title
                      "Height",           // X-Axis label
                      "Weight",           // Y-Axis label
                      xyDataset,          // Dataset
                      true                // Show legend
                     );