Creating Gantt Chart In Java Using JFreeChart API [Example/Tutorial]

In a row of writing tutorials about creating various charts using JFreeChart, I am writing on how to create Gantt Charts.

About Gantt Charts:

A Gantt chart is a type of bar chart that illustrates a project schedule. Gantt charts illustrate the start and finish dates of the terminal elements and summary elements of a project. Terminal elements and summary elements comprise the work breakdown structure of the project. Some Gantt charts also show the dependency (i.e, precedence network) relationships between activities. Gantt charts can be used to show current schedule status using percent-complete shadings and a vertical “TODAY” line.

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Although now regarded as a common charting technique, Gantt charts were considered revolutionary when they were introduced. In recognition of Henry Gantt’s contributions, the Henry Laurence Gantt Medal is awarded for distinguished achievement in management and in community service. This chart is used also in Information Technology to represent data that has been collected.

Gantt charts have become a common technique for representing the phases and activities of a project work breakdown structure (WBS), so they can be understood by a wide audience.

A common error made by those who equate Gantt chart design with project design is that they attempt to define the project work breakdown structure at the same time that they define schedule activities. This practice makes it very difficult to follow the 100% Rule. Instead the WBS should be fully defined to follow the 100% Rule, then the project schedule can be designed.

Although a Gantt chart is useful and valuable for small projects that fit on a single sheet or screen, they can become quite unwieldy for projects with more than about 30 activities. Larger Gantt charts may not be suitable for most computer displays. A related criticism is that Gantt charts communicate relatively little information per unit area of display. That is, projects are often considerably more complex than can be communicated effectively with a Gantt chart.

Gantt charts only represent part of the triple constraints of projects, because they focus primarily on schedule management. Moreover, Gantt charts do not represent the size of a project or the relative size of work elements, therefore the magnitude of a behind-schedule condition is easily miscommunicated. If two projects are the same number of days behind schedule, the larger project has a larger impact on resource utilization, yet the Gantt does not represent this difference.

Although project management software can show schedule dependencies as lines between activities, displaying a large number of dependencies may result in a cluttered or unreadable chart.

Because the horizontal bars of a Gantt chart have a fixed height, they can misrepresent the time-phased workload (resource requirements) of a project. In the example shown in this article, Activities E and G appear to be the same size, but in reality they may be orders of magnitude different. A related criticism is that all activities of a Gantt chart show planned workload as constant. In practice, many activities (especially summary elements) have front-loaded or back-loaded work plans, so a Gantt chart with percent-complete shading may actually miscommunicate the true schedule performance status. [Wikipedia/Creative Commons Attribution-ShareAlike License]

About JFreeChart:
JFreeChart is an open-source framework for the programming language Java, which allows the creation of complex charts in a simple way.

JFreeChart also works with GNU Classpath, a free software implementation of the standard class library for the Java programming language.

Following chart types are supported:

  • * X-Y charts (line, spline and scatter)
  • * Pie charts
  • * Gantt charts
  • * Bar charts (horizontal and vertical, stacked and independent)
  • * Single valued (thermometer, compass, speedometer)

Downloading JFreeChart API:
You can download the JFreeChart API required for this tutorial in their official website www.jfree.org

Working Java Example Code:
I wrote, compiled and tested the following code that generates and saves Gantt Charts using JFreeChart API. The generated sample Gantt Chart is at the end of the code.

package com.kushal.charts;
/**
 * @Author Kushal Paudyal
 * www.sanjaal.com/java
 * Last Modified On: 2009-September 25
 *
 * Demonstrating the use of JFreeChart to create
 * Gantt Chart
 **/

import java.io.File;
import java.io.IOException;
import java.util.Calendar;
import java.util.Date;

import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartUtilities;
import org.jfree.chart.JFreeChart;
import org.jfree.data.category.IntervalCategoryDataset;
import org.jfree.data.gantt.Task;
import org.jfree.data.gantt.TaskSeries;
import org.jfree.data.gantt.TaskSeriesCollection;
import org.jfree.data.time.SimpleTimePeriod;

public class MyGanttChart {

private static final long serialVersionUID = 3488074583840465632L;

public static IntervalCategoryDataset createDataset() {

/**
* Creating a task series
* And adding planned tasks dates on the series.
*/
TaskSeries seriesOne = new TaskSeries("Planned Implementation");

/**Adding data in this series**/
seriesOne.add(new Task("Sanjaal Domain Registration",
new SimpleTimePeriod(makeDate(10, Calendar.JUNE, 2007),
makeDate(15, Calendar.JUNE, 2007))));

seriesOne.add(new Task("Feature Addition - Java Blog",
new SimpleTimePeriod(makeDate(9, Calendar.JULY, 2007),
makeDate(19, Calendar.JULY, 2007))));

seriesOne.add(new Task("Feature Addition - PHPBB Forum",
new SimpleTimePeriod(makeDate(10, Calendar.AUGUST, 2007),
makeDate(15, Calendar.AUGUST, 2007))));

seriesOne.add(new Task("Feature Addition - Tagged Mails",
new SimpleTimePeriod(makeDate(6, Calendar.MAY, 2007), makeDate(
30, Calendar.MAY, 2007))));

seriesOne.add(new Task("Feature Addition - H1B Visa Portal",
new SimpleTimePeriod(makeDate(2, Calendar.JUNE, 2007),
makeDate(2, Calendar.JUNE, 2007))));

seriesOne.add(new Task("Feature Addition - Events Gallery",
new SimpleTimePeriod(makeDate(3, Calendar.JUNE, 2007),
makeDate(31, Calendar.JULY, 2007))));

seriesOne.add(new Task("Google Adsense Integration",
new SimpleTimePeriod(makeDate(1, Calendar.AUGUST, 2007),
makeDate(8, Calendar.AUGUST, 2007))));

seriesOne.add(new Task("Adbrite Advertisement Integration",
new SimpleTimePeriod(makeDate(10, Calendar.AUGUST, 2007),
makeDate(10, Calendar.AUGUST, 2007))));

seriesOne.add(new Task("InfoLink Advertisement Integration",
new SimpleTimePeriod(makeDate(12, Calendar.AUGUST, 2007),
makeDate(12, Calendar.SEPTEMBER, 2007))));

seriesOne.add(new Task("Feature Testing", new SimpleTimePeriod(
makeDate(13, Calendar.SEPTEMBER, 2007), makeDate(31,
Calendar.OCTOBER, 2007))));

seriesOne.add(new Task("Public Release", new SimpleTimePeriod(makeDate(
1, Calendar.NOVEMBER, 2007), makeDate(15, Calendar.NOVEMBER,
2007))));

seriesOne.add(new Task("Post Release Bugs Collection",
new SimpleTimePeriod(makeDate(28, Calendar.NOVEMBER, 2007),
makeDate(30, Calendar.NOVEMBER, 2007))));

/**
* Creating another task series
*/
TaskSeries seriesTwo = new TaskSeries("Actual Implementation");

/**Adding data in this series**/
seriesTwo.add(new Task("Sanjaal Domain Registration",
new SimpleTimePeriod(makeDate(11, Calendar.JUNE, 2007),
makeDate(14, Calendar.JUNE, 2007))));

seriesTwo.add(new Task("Feature Addition - Java Blog",
new SimpleTimePeriod(makeDate(11, Calendar.JULY, 2007),
makeDate(19, Calendar.JULY, 2007))));

seriesTwo.add(new Task("Feature Addition - PHPBB Forum",
new SimpleTimePeriod(makeDate(10, Calendar.AUGUST, 2007),
makeDate(17, Calendar.AUGUST, 2007))));

seriesTwo.add(new Task("Feature Addition - Tagged Mails",
new SimpleTimePeriod(makeDate(7, Calendar.MAY, 2007), makeDate(
1, Calendar.JUNE, 2007))));

seriesTwo.add(new Task("Feature Addition - H1B Visa Portal",
new SimpleTimePeriod(makeDate(2, Calendar.JUNE, 2007),
makeDate(4, Calendar.JUNE, 2007))));

seriesTwo.add(new Task("Feature Addition - Events Gallery",
new SimpleTimePeriod(makeDate(3, Calendar.JUNE, 2007),
makeDate(13, Calendar.JULY, 2007))));

seriesTwo.add(new Task("Google Adsense Integration",
new SimpleTimePeriod(makeDate(2, Calendar.AUGUST, 2007),
makeDate(7, Calendar.AUGUST, 2007))));

seriesTwo.add(new Task("Adbrite Advertisement Integration",
new SimpleTimePeriod(makeDate(10, Calendar.AUGUST, 2007),
makeDate(11, Calendar.AUGUST, 2007))));

seriesTwo.add(new Task("InfoLink Advertisement Integration",
new SimpleTimePeriod(makeDate(13, Calendar.AUGUST, 2007),
makeDate(15, Calendar.SEPTEMBER, 2007))));

seriesTwo.add(new Task("Feature Testing", new SimpleTimePeriod(
makeDate(13, Calendar.SEPTEMBER, 2007), makeDate(3,
Calendar.NOVEMBER, 2007))));

seriesTwo.add(new Task("Public Release", new SimpleTimePeriod(makeDate(
4, Calendar.NOVEMBER, 2007), makeDate(15, Calendar.NOVEMBER,
2007))));

seriesTwo.add(new Task("Post Release Bugs Collection",
new SimpleTimePeriod(makeDate(28, Calendar.NOVEMBER, 2007),
makeDate(3, Calendar.DECEMBER, 2007))));

final TaskSeriesCollection collection = new TaskSeriesCollection();

/**
* Adding the series to the collection
* Holds actual Dates.
*/
collection.add(seriesOne);
collection.add(seriesTwo);

return collection;
}

private static Date makeDate(final int day, final int month, final int year) {

final Calendar calendar = Calendar.getInstance();
calendar.set(year, month, day);
final Date result = calendar.getTime();
return result;

}

/**
* Creates a Gantt chart based on input data set
*/
private JFreeChart createChart(final IntervalCategoryDataset dataset) {
final JFreeChart chart = ChartFactory.createGanttChart(
"Gantt Chart - Sanjaal.com Feature Implmentation", // chart title
"Task", // domain axis label
"Date", // range axis label
dataset, // data
true, // include legend
true, // tooltips
false // urls
);
return chart;

}

public void saveChart(JFreeChart chart, String fileLocation) {
String fileName = fileLocation;
try {
/**
* This utility saves the JFreeChart as a JPEG First Parameter:
* FileName Second Parameter: Chart To Save Third Parameter: Height
* Of Picture Fourth Parameter: Width Of Picture
*/
ChartUtilities.saveChartAsJPEG(new File(fileName), chart, 800, 600);
} catch (IOException e) {
e.printStackTrace();
System.err.println("Problem occurred creating chart.");
}
}

/**
* Testing the Gantt Chart Creation
*/
public static void main(final String[] args) {

final MyGanttChart chartCreator = new MyGanttChart();
System.out.println("...Creating Dataset");
IntervalCategoryDataset dataset = createDataset();

System.out.println("...Creating Chart");
JFreeChart chart = chartCreator.createChart(dataset);

String fileName = "C:/temp/myGantChartDemo.jpg";

System.out.println("...Saving the Chart");
chartCreator.saveChart(chart, fileName);

System.out.println("...Chart Created Successfully and Saved");
System.out.println("Output Chart File Location: " + fileName);

}
}

The following is the output of running this program:

...Creating Dataset
...Creating Chart
...Saving the Chart
...Chart Created Successfully and Saved
Output Chart File Location: C:/temp/myGantChartDemo.jpg

The following is the Gantt Chart generated by the Java Program above.

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