JFreeChart is a big library, but we work hard to make it use sensible
defaults so that you don't have to write a lot of code to get great
looking charts.  For example, here is a scatter plot demo written using
the JFreeChart API:

import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.data.xy.XYSeries;
import org.jfree.data.xy.XYSeriesCollection;
import org.jfree.ui.ApplicationFrame;
import org.jfree.ui.RefineryUtilities;

public class ScatterPlotDemo extends ApplicationFrame {

    public ScatterPlotDemo(String title) {

        super(title);

        XYSeriesCollection dataset = new XYSeriesCollection();

        XYSeries series1 = new XYSeries("Series 1");
        series1.add(1.0, 4.5);
        series1.add(4.4, 3.2);
        dataset.addSeries(series1);

        XYSeries series2 = new XYSeries("Series 2");
        series2.add(3.2, 8.5);
        series2.add(4.9, 3.7);
        dataset.addSeries(series2);

        JFreeChart chart = ChartFactory.createScatterPlot(
            "Scatter Plot Demo",  // title
            "X", "Y",             // axis labels
            dataset,              // dataset
            PlotOrientation.VERTICAL,
            true,                 // legend? yes
            true,                 // tooltips? yes
            false                 // URLs? no
        );
        ChartPanel chartPanel = new ChartPanel(chart);
        chartPanel.setPreferredSize(new java.awt.Dimension(500, 270));
        setContentPane(chartPanel);

    }

    public static void main(String[] args) {
        ScatterPlotDemo demo = new ScatterPlotDemo("Scatter Plot Demo");
        demo.pack();
        RefineryUtilities.centerFrameOnScreen(demo);
        demo.setVisible(true);
    }

}

I hope you'll give JFreeChart a try!

Regards,

Dave Gilbert
JFreeChart Project Leader

Pipe the data into good olf gnuplot if you can live with an non all-Java
 solution and a separate application.

/Thomas