import java.awt.*;import java.awt.event.*;import javax.swing.*;import org.jfree.chart.ChartPanel;import org.jfree.chart.JFreeChart;import org.jfree.chart.axis.DateAxis;import org.jfree.chart.axis.NumberAxis;import org.jfree.chart.plot.XYPlot;import org.jfree.chart.renderer.xy.XYItemRenderer;import org.jfree.chart.renderer.xy.XYLineAndShapeRenderer;import org.jfree.data.time.*;import org.jfree.ui.RectangleInsets;public class MemoryUsageDemo extends JPanel{    class DataGenerator extends Timer        implements ActionListener    {        public void actionPerformed(ActionEvent actionevent)        {            long l = Runtime.getRuntime().freeMemory();            long l1 = Runtime.getRuntime().totalMemory();            addTotalObservation(l1);            addFreeObservation(l);        }        DataGenerator(int i)        {            super(i, null);            addActionListener(this);        }    }    public MemoryUsageDemo(int i)    {        super(new BorderLayout());        total = new TimeSeries("Total Memory", org.jfree.data.time.Millisecond.class);        total.setMaximumItemAge(i);        free = new TimeSeries("Free Memory", org.jfree.data.time.Millisecond.class);        free.setMaximumItemAge(i);        TimeSeriesCollection timeseriescollection = new TimeSeriesCollection();        timeseriescollection.addSeries(total);        timeseriescollection.addSeries(free);        DateAxis dateaxis = new DateAxis("Time");        NumberAxis numberaxis = new NumberAxis("Memory");        dateaxis.setTickLabelFont(new Font("SansSerif", 0, 12));        numberaxis.setTickLabelFont(new Font("SansSerif", 0, 12));        dateaxis.setLabelFont(new Font("SansSerif", 0, 14));        numberaxis.setLabelFont(new Font("SansSerif", 0, 14));        XYLineAndShapeRenderer xylineandshaperenderer = new XYLineAndShapeRenderer(true, false);        xylineandshaperenderer.setSeriesPaint(0, Color.red);        xylineandshaperenderer.setSeriesPaint(1, Color.green);        xylineandshaperenderer.setSeriesStroke(0, new BasicStroke(3F, 0, 2));        xylineandshaperenderer.setSeriesStroke(1, new BasicStroke(3F, 0, 2));        XYPlot xyplot = new XYPlot(timeseriescollection, dateaxis, numberaxis, xylineandshaperenderer);        xyplot.setBackgroundPaint(Color.lightGray);        xyplot.setDomainGridlinePaint(Color.white);        xyplot.setRangeGridlinePaint(Color.white);        xyplot.setAxisOffset(new RectangleInsets(5D, 5D, 5D, 5D));        dateaxis.setAutoRange(true);        dateaxis.setLowerMargin(0.0D);        dateaxis.setUpperMargin(0.0D);        dateaxis.setTickLabelsVisible(true);        numberaxis.setStandardTickUnits(NumberAxis.createIntegerTickUnits());        JFreeChart jfreechart = new JFreeChart("JVM Memory Usage", new Font("SansSerif", 1, 24), xyplot, true);        jfreechart.setBackgroundPaint(Color.white);        ChartPanel chartpanel = new ChartPanel(jfreechart, true);        chartpanel.setBorder(BorderFactory.createCompoundBorder(BorderFactory.createEmptyBorder(4, 4, 4, 4), BorderFactory.createLineBorder(Color.black)));        add(chartpanel);    }    private void addTotalObservation(double d)    {        total.add(new Millisecond(), d);    }    private void addFreeObservation(double d)    {        free.add(new Millisecond(), d);    }    public static void main(String args[])    {        JFrame jframe = new JFrame("Memory Usage Demo");        MemoryUsageDemo memoryusagedemo = new MemoryUsageDemo(30000);        jframe.getContentPane().add(memoryusagedemo, "Center");        jframe.setBounds(200, 120, 600, 280);        jframe.setVisible(true);        (memoryusagedemo. new DataGenerator(100)).start();        jframe.addWindowListener(new WindowAdapter() {            public void windowClosing(WindowEvent windowevent)            {                System.exit(0);            }        });    }    private TimeSeries total;    private TimeSeries free;}     以上的代码如果运行的话就成为一个很好的时序图了。可以动态显示 出来电脑内存的变化情况。    好好研究一下其代码。