drawing a diagram with JFreeChart

Question

I'm working with jFreeChart on Eclipse (in Windows) and I want to draw gantt diagram for processors.
I'm doing a XY Chart

But my programme draw me a line with only P0. I want something like

• draw from 0 to 10 --> P0
• then from 10 to 20 --> draw H
• then from 20 to 30 ---->draw wait
• from 30 to 40---> draw P0
• from 35 to 40 -->draw H

Code:

    import javax.swing.JFrame;
    import org.jfree.chart.ChartFactory;
    import org.jfree.chart.ChartPanel;
    import org.jfree.chart.JFreeChart;
    import org.jfree.chart.plot.PlotOrientation;
    import org.jfree.data.xy.XYDataset;
    import org.jfree.data.xy.XYSeries;
    import org.jfree.data.xy.XYSeriesCollection;

    public class JFreeChartLineChartExample extends JFrame {

    private static final long serialVersionUID = 1L;

    public JFreeChartLineChartExample(String applicationTitle, String chartTitle) {
    super(applicationTitle);

    // based on the dataset we create the chart
    JFreeChart pieChart = ChartFactory.createXYLineChart(chartTitle, "Time", "Processors",    
      createDataset(),PlotOrientation.VERTICAL, true, true, false);

    // Adding chart into a chart panel
    ChartPanel chartPanel = new ChartPanel(pieChart);

    // settind default size
    chartPanel.setPreferredSize(new java.awt.Dimension(500, 270));

    // add to contentPane
    setContentPane(chartPanel);
    }

    private XYDataset createDataset() {

  final XYSeries P0 = new XYSeries("P0");
  P0.add(0, 1);
  P0.add(10, 1);

  P0.add(35, 1);
  P0.add(50, 1);
  P0.add(85, 1);
  P0.add(110, 1);


  final XYSeries P2 = new XYSeries("P2");



  final XYSeries P1 = new XYSeries("P1");



  final XYSeries H = new XYSeries("H");
  H.add(10, 1);
  H.add(20, 1);
  H.add(45, 1);
  H.add(100, 1);


  final XYSeries wait = new XYSeries("wait");
  wait.add(80, 1);
  wait.add(90, 1);
  wait.add(105, 1);



  final XYSeriesCollection dataset = new XYSeriesCollection();
  dataset.addSeries(P0);
  dataset.addSeries(P2);
  dataset.addSeries(P1);
  dataset.addSeries(H);
  dataset.addSeries(wait);

  return dataset;

       }

   public static void main(String[] args) {
  JFreeChartLineChartExample chart = new JFreeChartLineChartExample(" GANTT ", " GANTT");
  chart.pack();
  chart.setVisible(true);
     }
   }

Answer 1

As far as I have understood you want to have gaps in your datasets. Your code paints a straight line from time 0 to 110 for dataset P0 because JFreeChart does not know that you want to have gaps.

To add gaps you need to add null values to your datasets.

For example P0 should be created as follows:

final XYSeries P0 = new XYSeries("P0");
P0.add(0, 1);
P0.add(10, 1);
P0.add(11, null);
P0.add(35, 1);
P0.add(50, 1);
P0.add(51, null);
P0.add(85, 1);
P0.add(110, 1);

You might also have a look at the special Gantt classes provided by JFreeChart. There are some examples in the JFreeChart demo.