JAVA生成堆积图

Java源码：
package Test.JFreeChar;

import java.awt.Color;
import java.awt.Component;
import java.awt.Font;
import java.io.File;
import java.io.FileOutputStream;
import java.text.DecimalFormat;

import javax.swing.JFrame;

import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.ChartUtilities;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.axis.CategoryAxis;
import org.jfree.chart.axis.NumberAxis;
import org.jfree.chart.axis.ValueAxis;
import org.jfree.chart.plot.CategoryPlot;
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.chart.renderer.category.StackedBarRenderer;
import org.jfree.chart.title.TextTitle;
import org.jfree.data.category.CategoryDataset;
import org.jfree.data.general.DatasetUtilities;

public class JfreechartStack extends JFrame{
    private static final long serialVersionUID = 1L;
    private static final String CHART_PATH = "pic/";
    JfreechartStack(){

        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setTitle("JFreeChart堆积图");
        this.add(CreateMainPanel());
        this.pack();
        this.setVisible(true);
    }
    private Component CreateMainPanel() {
        CategoryDataset dataset = prepareDataset();
        JFreeChart chart=createJFreeChart(dataset, "x坐标", "y坐标", "堆积图");
        return new ChartPanel(chart);
    }
    public static void main(String[] args) {
        new JfreechartStack().makeStackedBarChart();
    }

    /**
     * 生成堆栈柱状图
     */
    public void makeStackedBarChart() {
        CategoryDataset dataset = prepareDataset();
        saveAsFile("stsckedBar.png",createJFreeChart(dataset,
                "x坐标", "y坐标", "堆积图"));
    }
    private CategoryDataset prepareDataset() {
        double[][] data = new double[][] {
                { 0.21, 0.66, 0.23, 0.40, 0.26 },
                { 0.25, 0.21, 0.10, 0.40, 0.16 }
                };
        String[] rowKeys = { "苹果", "梨子" };
        String[] columnKeys = { "北京", "上海", "广州", "成都", "深圳" };