Atualizar Gráfico jfreeChart com dados dentro de um arquivo txt

public class Velocimetro extends JFrame {  
      
        private static String velocidadeValor = "0";  
      
        private static JFreeChart jfreechart;
        
        public static String getVelocidadeValor() {  
            return velocidadeValor;  
        }  
      
        public static void setVelocidadeValor(String velocidade) {  
            velocidadeValor = velocidade;  
        }  
        public static DefaultValueDataset dataset;  
      
        public static void setDefaultValueDataSet(DefaultValueDataset data) {  
            dataset = data;  
        }  
      
        public static DefaultValueDataset getDefaultValueDataSet() {  
            return dataset;  
        }  
      
        public static class DemoPanel extends JPanel //implements FocusListener//ChangeListener  
        {  
            JSlider slider;  
            DefaultValueDataset xdataset;  
      
            public static JFreeChart createStandardDialChart(String s, String s1, ValueDataset valuedataset, double d, double d1, double d2, int i) {  
                DialPlot dialplot = new DialPlot();  
                dialplot.setDataset(valuedataset);  
                dialplot.setDialFrame(new StandardDialFrame());  
                dialplot.setBackground(new DialBackground());  
                DialTextAnnotation dialtextannotation = new DialTextAnnotation(s1);  
                dialtextannotation.setFont(new Font("Dialog", 1, 14));  
                dialtextannotation.setRadius(0.69999999999999996D);  
                dialplot.addLayer(dialtextannotation);  
                DialValueIndicator dialvalueindicator = new DialValueIndicator(0);  
                dialplot.addLayer(dialvalueindicator);  
                StandardDialScale standarddialscale = new StandardDialScale(d, d1, -120D, -300D, 10D, 4);  
                standarddialscale.setMajorTickIncrement(d2);  
                standarddialscale.setMinorTickCount(i);  
                standarddialscale.setTickRadius(0.88D);  
                standarddialscale.setTickLabelOffset(0.14999999999999999D);  
                standarddialscale.setTickLabelFont(new Font("Dialog", 0, 14));  
                dialplot.addScale(0, standarddialscale);  
                dialplot.addPointer(new org.jfree.chart.plot.dial.DialPointer.Pin());  
                DialCap dialcap = new DialCap();  
                dialplot.setCap(dialcap);  
                return new JFreeChart(s, dialplot);  
            }  
      
            public DemoPanel() throws InterruptedException, FileNotFoundException, IOException {  
      
                xdataset = new DefaultValueDataset(Integer.parseInt(velocidadeValor));  
                System.out.println("O valor xdataset = " + xdataset.getValue());  
      
                jfreechart = createStandardDialChart(  
                        "Velocidade",   //Título do gráfico
                        "Km/h",         //Unidade de medida do gráfico
                        xdataset,       //Valor indicado no velocímetro
                        0D,             //Marcador Mínimo do velocímetro
                        200D,           //Marcador Máximo do velocímetro
                        10D,            //Marcador da medida (proporção)
                        10);            //Divisões do mostrador de medida
      
                //indicativo das cores (VERMELHO, VERDE E AMARELO)
                DialPlot dialplot = (DialPlot) jfreechart.getPlot();  
                StandardDialRange standarddialrange = new StandardDialRange(120D, 200D, Color.red);  
                standarddialrange.setInnerRadius(0.52000000000000002D);  
                standarddialrange.setOuterRadius(0.55000000000000004D);  
                dialplot.addLayer(standarddialrange);  
                StandardDialRange standarddialrange1 = new StandardDialRange(100D, 120D, Color.yellow);  
                standarddialrange1.setInnerRadius(0.52000000000000002D);  
                standarddialrange1.setOuterRadius(0.55000000000000004D);  
                dialplot.addLayer(standarddialrange1);  
                StandardDialRange standarddialrange2 = new StandardDialRange(0D, 100D, Color.green);  
                standarddialrange2.setInnerRadius(0.52000000000000002D);  
                standarddialrange2.setOuterRadius(0.55000000000000004D);  
                dialplot.addLayer(standarddialrange2);  
      
                GradientPaint gradientpaint = new GradientPaint(new Point(), new Color(255, 255, 255), new Point(), new Color(170, 170, 220));  
                DialBackground dialbackground = new DialBackground(gradientpaint);  
                dialbackground.setGradientPaintTransformer(new StandardGradientPaintTransformer(GradientPaintTransformType.VERTICAL));  
                dialplot.setBackground(dialbackground);  
      
                //Ponteiro
                dialplot.removePointer(0);  
                org.jfree.chart.plot.dial.DialPointer.Pointer pointer = new org.jfree.chart.plot.dial.DialPointer.Pointer();  
                pointer.setFillPaint(Color.blue);  
                dialplot.addPointer(pointer);  
      
                ChartPanel chartpanel = new ChartPanel(jfreechart);  
                chartpanel.setPreferredSize(new Dimension(400, 400));  
      
                add(chartpanel); 
            }  
        }  
      
        public Velocimetro(String s) throws FileNotFoundException, IOException, InterruptedException {  
            super(s);  
            setDefaultCloseOperation(3);  
            setContentPane(createDemoPanel());  
        }  
      
        
        public void atualizaVelocimetro() throws IOException, FileNotFoundException, InterruptedException{
            setDefaultCloseOperation(3);  
            setContentPane(createDemoPanel());
        }
        
        public static JPanel createDemoPanel() throws FileNotFoundException, IOException, InterruptedException {  
            BufferedReader leitor = new BufferedReader(new FileReader("C:\\temp\\velocidade.txt"));  
            velocidadeValor = leitor.readLine();  
            return new DemoPanel();  
        }  
      
        public void lerVelocidadeTxt() throws FileNotFoundException, IOException, InterruptedException {  
            try {  
                BufferedReader leitor = new BufferedReader(new FileReader("C:\\temp\\velocidade.txt"));  
                velocidadeValor = leitor.readLine();  
            } catch (IOException e) {  
                System.out.println("Nao encontrou o arquivo velocidade.txt===========");  
            }  
      
            DemoPanel d = new DemoPanel();  
            d.validate();  
            System.out.println("Cheguei aqui dentro............" + Velocimetro.getVelocidadeValor());  
            
        }
    /**
     *
     * @throws java.io.IOException
     */
    public void tempoRel() throws IOException {  
            try {  
                Thread.sleep(5000);  
                atualizaVelocimetro();
            } catch (InterruptedException e) {  
                System.out.println("Nao leu o arquivo===========");  
      
            }  
        }  
    }

public class TestaVelocimetro {

    public static void main(String[] args) throws FileNotFoundException, IOException, InterruptedException {
        Velocimetro velocimetro = new Velocimetro("Velocímetro - Teste 1");
        velocimetro.pack();
        velocimetro.setVisible(true);
        while (true) {
            velocimetro.lerVelocidadeTxt();
            velocimetro.tempoRel();
            velocimetro.pack();
        }
    }

}