以编程方式检查堆

Question

我想像JConsole那样监视堆内存。我正在运行以下程序，每一秒后我都希望看到堆增长，因为我在每个回合中创建20个线程，但它没有在图中增长。请告诉我如何通过java程序检查堆内存。

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import org.jfree.chart.*;
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.*;    
public class MemoryUsageProgram extends JPanel
{
        class DataGenerator extends Timer
                implements ActionListener
        {

                public void actionPerformed(ActionEvent actionevent)
                {
                    for(int i=1;i<20;i++) {
                        IoBoundJob job=new IoBoundJob();
                        job.start();
                    }

                    System.gc();
                    long l = Runtime.getRuntime().freeMemory();
                    long l1 = Runtime.getRuntime().totalMemory();
                    long usedMB = (l1 - l)/1024/1024 ;
                    plotUsedMemory(usedMB);
                }

                DataGenerator(int i)
                {
                        super(i, null);
                        addActionListener(this);
                }
        }


        private TimeSeries used;

        public MemoryUsageProgram()
        {
                super(new BorderLayout());

                used = new TimeSeries("used");
                TimeSeriesCollection timeseriescollection = new TimeSeriesCollection();
                timeseriescollection.addSeries(used);
                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);
                dateaxis.setAutoRange(true);
                dateaxis.setLowerMargin(0.0D);
                dateaxis.setUpperMargin(0.0D);
                dateaxis.setTickLabelsVisible(true);
                numberaxis.setStandardTickUnits(NumberAxis.createIntegerTickUnits());
                JFreeChart jfreechart = new JFreeChart("Memory Usage", new Font("SansSerif", 1, 24), xyplot, true);
                ChartUtilities.applyCurrentTheme(jfreechart);
                ChartPanel chartpanel = new ChartPanel(jfreechart, true);
                chartpanel.setBorder(BorderFactory.createCompoundBorder(BorderFactory.createEmptyBorder(4, 4, 4, 4), BorderFactory.createLineBorder(Color.black)));
                add(chartpanel);
        }



        private void plotUsedMemory(double d)
        {
                used.add(new Millisecond(), d);
        }

        public static void main(String args[])
        {
                JFrame jframe = new JFrame("Memory Usage");
                MemoryUsageProgram memoryusagedemo = new MemoryUsageProgram();
                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);
                        }

                });       
        }
}

import java.util.concurrent.TimeUnit;

public class IoBoundJob  extends Thread {

    public IoBoundJob() {
    }

    @Override
    public void run() {
        try{
            Thread.currentThread().sleep(250);
        } catch(InterruptedException e) {
            System.out.println("from IOBoundJob Class");
        }
    }
}