Making XY line chart with string and double axis

import java.io.File;
import java.io.IOException;
import java.util.Date;
import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartUtilities;
import org.jfree.chart.JFreeChart;
import org.jfree.data.time.Day;
import org.jfree.data.time.TimeSeries;
import org.jfree.data.time.TimeSeriesCollection;

public class XYJfreechart {

   public static void main(String args []){

        TimeSeries series = new TimeSeries( "", Day.class );
        series.add(new Day(new Date("2012/03/01")), 50);
        series.add(new Day(new Date("2012/03/02")), 40);
        series.add(new Day(new Date("2012/03/03")), 30);
        series.add(new Day(new Date("2012/03/04")), 35);
        series.add(new Day(new Date("2012/03/05")), 20);
        series.add(new Day(new Date("2012/03/06")), 25);
        series.add(new Day(new Date("2012/03/07")), 32);

        TimeSeriesCollection dataset=new TimeSeriesCollection();
        dataset.addSeries(series);

        JFreeChart chart = ChartFactory.createTimeSeriesChart
        ("User Participation Chart",    
         "Day",                    
         "Temperature",            
         dataset,               
         true,                     
         true,              
         false              
        );

      try {
            ChartUtilities.saveChartAsJPEG(new File("c:/chart.jpg"), chart, 800, 600);
            System.out.println("Chart is created successfully.");
           } catch (IOException e) {
            e.printStackTrace();
            System.err.println("Problem occurred creating chart.");
        }
    }
}

Okay, I tried to make it work, but it just leaves me with a bunch of error messages. The JPanel looks like this:

    print("private JPanel createGraphArea() throws ClassNotFoundException, FileNotFoundException, IOException, ParseException {

        JPanel graph = new JPanel();
        graph.setLayout(new java.awt.BorderLayout());

        ArrayList<Double> graphtemperature = new ArrayList<Double>();
        ArrayList<Date> clockset = new ArrayList<Date>();
        SimpleDateFormat dt = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

        for (int i = 0; i < data.size(); i++) {
            String sp = data.get(i);
            String[] tokens = sp.split("\t");
            if (tokens.length == 2) {
                Date date = dt.parse(tokens[0]);
                clockset.add(date);
                graphtemperature.add(Double.parseDouble(tokens[1]));
            }

        }
        TimeSeries series = new TimeSeries("",Day.class);
        for(int i = 0; i < data.size(); i++){
            series.add(new Day(clockset.get(i)), graphtemperature.get(i));
        }

        TimeSeriesCollection dataset = new TimeSeriesCollection();
        dataset.addSeries(series);

        JFreeChart chart = ChartFactory.createTimeSeriesChart(null, 
                "Time", 
                "Temperature", 
                dataset, 
                true, 
                true,
                false);

        ChartPanel CP = new ChartPanel(chart);
        graph.add(CP, BorderLayout.CENTER);
        graph.validate();*/

        return graph;
    }");

And the error messages:

    print("Exception in thread "main" java.lang.NoClassDefFoundError: org/jfree/date/MonthConstants
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
    at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
Caused by: java.lang.ClassNotFoundException: org.jfree.date.MonthConstants
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
    ... 12 more
Java Result: 1");

Somehow I think the error is at Day.class?