用jfreechart的在jpanel中添加图表的有关问题

    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                                 DefaultCategoryDataset DataSet = new DefaultCategoryDataset();        DataSet.addValue(300, "number", "apple");        DataSet.addValue(400, "number", "barara");        DataSet.addValue(250, "number", "pear");        DataSet.addValue(330, "number", "milk");        DataSet.addValue(420, "number", "cheese");        //创建柱形图        JFreeChart chart = ChartFactory.createBarChart3D("Catogram",                "Fruit", "Sale", DataSet, PlotOrientation.VERTICAL,                false, false, false);        //用来放置图表        ChartPanel panel = new ChartPanel(chart);              jPanel10.add(10); //jPanel10是我已经添加好的面板            }