Introduction to JUnit

In this post we will start to learn about JUnit Framework. JUnit is a framework for unit testing Java applications. It was developed by Kent Back and Erich Gamma to help developers to create a better applications. JUnit has become the standard tool used by developers when it comes to unit testing.

Everyday, when you create an application from the smallest one, that consist of a single class to a project of a large application, your development workflow will always be the same. You will begin by writing a small code, compile it, run the code and finally test it. And you will mostly find that things doesn’t work as expected at first. So you’ll go back to your favorite IDE, check what the error was and you will repeat the process, code, compile, run and test, until you get the result that you want.

We can do this steps manually. For example when you have a console application you will typically run the code, check the result printed out on the console screen to find out if the program return the correct result. When you find the error you will fix it and re-run the code again and again. This kind of test seems like a time consuming activity, tiresome and even make you bored. And instead of testing the code you are testing your ability to test. Because you have to check whether the output printed in the console is correct or not.

Here is a simple example of a very simple calculator that know how to add two numbers and how you are testing it using a simple main class in a console application.

package org.kodejava.junit;

public class Calculator {
    public static int add(int a, int b) {
        return a + b;

    public static void main(String[] args) {
        int a = 10;
        int b = 15;
        int c = Calculator.add(a, b);

        System.out.println("a = " + a);
        System.out.println("b = " + b);
        System.out.println("c = " + c);

        if (c == 25) {
            System.out.println("Test success!");
        } else {
            System.out.println("Test failed!");
Testing your ability to test.

Testing your ability to test.

To make life easier JUnit framework comes with great help to overcome these problems. You can tell JUnit framework to test your code by creating a unit tests. You will create a class that test your code, you’ll define your testing criteria in this unit testing class. You can execute these unit testing and it will report whether the tests pass or fail. And you can run it as many time as you’ll like to see if the test still pass after you modified parts of your code.

Now, let see how JUnit can help us testing the previous calculator code. Before creating the unit test class we need to download the JUnit library from the website at JUnit, follow the link to download page and download the jars. There are two main jar files that you need to download, the junit.jar and  hamcrest-core.jar. When you are using and IDE, the JUnit usually installed as part of the IDE such as NetBeans, Eclipse or IntelliJ IDEA.

Let’s write the unit testing code.

package org.kodejava.junit;

import org.junit.Test;
import static junit.framework.Assert.*;

public class CalculatorTest {
    public void addTwoNumbersTest() {
        int a = 10;
        int b = 15;
        assertEquals(25, Calculator.add(a, b));

From this code snippet what you can see is:

  • We create a class called CalculatorTest. We usually name the unit test class with the same name with the class under test but suffix it with Test.
  • We create a test method called addTwoNumberTest(). You can name your test method as descriptive as possible. This will have you understand what the method is trying to test.
  • To make a method a unit test method we add the @Test annotation to it. This annotation will tell the JUnit framework that the annotated method is a part of the unit testing it should execute on our behalf.
  • In the test method body we use the assertEquals() method to check the test result. In this case we expect 25 is returned when the Calculaor.add() method add two numbers, the a + b.

After you create the unit testing class, let’s compile it and this JUnit test from the command prompt. Remember to have also the class under test, which is the Calculator class beside your unit testing class. To execute JUnit test you can type the following command.

java -cp .;junit-4.10.jar org.junit.runner.JUnitCore org.kodejava.junit.CalculatorTest

I am intentionally place the junit.jar file in the root of my work directory so that I can make the -cp option short. The classpath options tell Java where to look the required class files.

Executing JUnit Test

Executing JUnit Test

That’s is all for the bit of introduction to JUnit. In the coming post I will write more about JUnit and how to use other available annotation so you can write a better test.

Introduction to GenMyModel

After 3 years of research and development, GenMyModel draws the future of software modeling. GenMyModel is a free browser hosted UML tool for developers and software architects. Its main strength: create UML compliant models online and generate code. Unlike the well known desktop alternatives, it allows you to work on any web browser and from any computer with any OS (Windows, Linux, Mac OS).

GenMyModel has been released in beta in 2013. It supports for now class and use case diagrams and works with GitHub to host the generated code. You can try GenMyModel here UML Online Tool.

Online UML Tool

Online UML Tool


Using the App

Log in & create an UML project

The application itself is available at this address: First thing you see is the connection window where you can sign in with your Google account or sign up with another mail address.

GenMyModel Dashboard

GenMyModel Dashboard

Once you are logged in, you discover your dashboard where you have the choice to create a new project or use one of the existing templates below. When you create a new project, you can then set a title and choose between a public or private project. When you open a project, a new tab appears above for you to easily switch between your class and use case

Public UML Online

Public UML Online


Creating class and use case diagrams

When you create a new project, it instantly opens a tab for class diagrams, but you can choose in the File menu to make new use case diagrams.

The vertical toolbar between your whiteboard and the project explorer shows you the different tools to create classes, interfaces, add attributes, make associations and more. For example, if you select the class tool or press ‘C’ (the underlined letters being keyboard shortcuts), you can place a class anywhere on your whiteboard. You can also add several elements at a time by holding Ctrl.

Class Diagram Online

Class Diagram Online

You can then select one or more elements and move them on your whiteboard, rearrange links or set a few properties. Same thing goes for use case diagrams.


Change the model properties

The bottom left corner of the application groups all the properties you need for the elements you selected. This way, this small window allows you to set names, types, visibility, multiplicity, comments and a few other settings.

UML Online Property

UML Online Property

Those possibilities change according to your selection on your whiteboard or the project explorer.


Code generation and push to GitHub

Generate Java and SQL code

GenMyModel provides code generators:

  • Java Beans
  • JPA Beans
  • Spring Data REST application
  • Spring Roo
  • SQL

There are two ways to generate code: with the ‘Tools’ menu or by right clicking on your model. You can then choose between a direct generation creating a ZIP file with Java, Java JPA or SQL code, or configuring your own saved configuration allowing you to push to your GitHub repositories.

UML Code Generators

UML Code Generators


Push to GitHub

If you are a GitHub user, you can push your generated code to the hosting service. In the code generation configuration window, you just have to type your repository URL and the branch you would like to send your code to. The first push can take a while but it is quite fast afterwards.

UML Java Code Generator

UML Java Code Generator


Report, image and model export

Export to image and XMI

GenMyModel allows you to export you models to image files in JPEG or SVG, or export to XMI. You can choose either format by rightclicking or with the ‘Tools’ menu.

Export documentation to PDF

You can also export the documentation of your models to a PDF file. Resulting in a document with images of your diagrams and the list of every element and its properties.

UML PDF Export

UML PDF Export


Share by email

Sharing to social network is planned for the next few months, in the meantime you can share your work by email with the same menu.

Web description for public projects

When creating a project within GenMyModel, you can choose between the public and private options. Private means only you can see and modify the model. Public means you are the only one allowed to modify it but anyone can fork it.

Web pages are automatically created for public projects so that you can share and show what you design. Examples: Class Diagram University Management System

What’s next

The next major release before October 2013 will include:

  • Realtime collaboration
  • Java Reverse engineering
  • Package support for class diagrams and use case diagrams


GenMyModel is built upon Javascript and HTML5.

Introduction to Apache Maven

In this post you will learn about Apache Maven. What is Maven? In simple words, Maven is a tool that we can use to build and manage a Java based project. Compare to the older type of build tool such as Ant, which is also an Apache project, Maven gives developers a standard way to build projects, a clear definition of the projects consisted of, an easy way to publish project information and an easy management of the project libraries dependency.

In Maven, the project libraries (Jars) will be maintained in the Maven repository and can be shared among projects. We don’t need to include the Jars in the project’s source code, as what we usually do when using tool like Ant. And here are the main objectives of the Apache Maven project:

  • Making the build process easy.
  • Providing a uniform build system.
  • Providing quality project information.
  • Providing guidelines for best practices development.
  • Allowing transparent migration to a new features.

After you know a little bit about Maven, let’s continue to the next step, installing the Apache Maven.

Step 1. Downloading Apache Maven

  • Go to Apache Maven and from the Get Maven section on the left sidebar click Download link.
  • Download the appropriate installer for your platform. For example I am downloading the .zip file. The latest version when this post is written is Maven 3.1.0 (
  • Extract the downloaded zip file. For example I am extracting it into D:\Toolbox\apache-maven-3.1.0 directory.

Step 2. Configuring Environment Variables

  • After extracting Maven distribution you have to define M2_HOME environment variable. The value of this variable is the path to your Maven installation.
  • You can create environment variable using the following steps:
    • Right click on My Computer.
    • Select Properties menu.
    • Select Advanced system settings.
    • In the System Properties window select the Advanced tab and click the Environment Variables button.
    • Add the variable in the System variables section.
    • Click OK to proceed.
  • Add the %M2_HOME%\bin; into your PATH environment variable so that you can execute Maven command from any path inside your command prompt. This PATH variable can also be updated in the System variables section.

  • Open your command prompt and type echo %M2_HOME%. Pressing Enter and you should see the value of the variable printed on the console. For example:
D:\>echo %M2_HOME%
  • To check if Maven also in your Path variable you can execute echo %PATH% in your command prompt. You should see the path to Maven binary in the Path variable.
D:\>echo %PATH%
D:\Toolbox\apache-maven-3.1.0\bin;C:\Program Files (x86)\Java\jdk1.7.0_13\bin;

Step 3. Running Maven

  • Now you have Maven installed and configured. Let’s run Maven for the first time.
  • To run Maven we use the mvn command.
  • For example to check the version of the Maven we run mvn -version
  • You will see the following output, more or less, it depends of the JDK version you have in your machine.
D:\>mvn -version
Apache Maven 3.1.0 (893ca28a1da9d5f51ac03827af98bb730128f9f2; 2013-06-28 10:15:32+0800)
Maven home: D:\Toolbox\apache-maven-3.1.0
Java version: 1.7.0_13, vendor: Oracle Corporation
Java home: C:Program Files (x86)\Java\jdk1.7.0_13\jre
Default locale: en_US, platform encoding: Cp1252
OS name: "windows 7", version: "6.1", arch: "x86", family: "windows"

Congratulations! You’ve install Apache Maven successfully on your development machine. On the next post I will show you how to create a new project using Maven.

Introduction to JetBrains IntelliJ IDEA Community Edition

In this post I will introduce to you the JetBrains IntelliJ IDEA, one the the most powerful IDE (Integrated Development Environment) for Java development or other languages that run on the JVM such as Groovy and Scala. IntelliJ IDEA comes in two editions, the IntelliJJ IDEA Ultimate Edition and the IntelliJ IDEA Community Edition.

The IntelliJ IDEA Community Edition is an open source version of Intelli JDEA. That’s mean you can use it for free. If you works with standard Java, Groovy, Scala or mobile development using Android then the Community Edition can be your choice. If you works with in web or Java EE development then the Ultimate Edition is the way to go.

Here are some features that you will get when using the IntelliJ IDEA Community Edition:

  • An Intelligent code editor that has all the smarts for understanding Java, XML and Groovy code.
  • Refactorings, code inspections and intentions, super-fast navigation and search
  • Testing frameworks integration: JUnit and TestNG
  • Build tools support: Ant and Maven
  • Popular version control systems integration: CVS, Subversion and Git
  • Swing UI designer

After a bit of introduction, let’s begin the installation.

Step 1. Getting the Installation Distribution

  • Download the installation package of the IntelliJ IDEA Community Edition.
  • Click Download IntelliJ IDEA Community Edition to go the the download page.
  • On the page you can see two editions, select the Community Edition. The current version available when this post was written is the version 12.1.4. You can also see that the download are available for Windows, Mac OS X and Linux. For this post I will download the Windows version. The download size for the Windows installer is around 130MB.

Step 2. Install IntelliJ IDEA Community Edition

  • To begin, double click the installer you’ve download, for example ideaIC-12.1.4.exe.
  • You’ll be greeted with the following screen

IntelliJ IDEA Setup Welcome Screen

  • Prest the Next button to continue.
  • You’ll be ask the installation location. On Windows it will be default to the C:\Program Files directory.
  • Press Next for a couple of times until the installation complete.
  • When you choose to run the IntelliJ IDEA for the first time you’ll get the following screen
Installation Complete Screen

Installation Complete Screen

  • Press OK button to start IntelliJ IDEA for the first time. You will be shown a splash screen right after you press the button and continued by the screen welcoming you to the IDE.
Welcome to IntelliJ IDEA

Welcome to IntelliJ IDEA

Step 3. Now you have the InteliJ IDEA Community Edition installed in your machine. Let’s create your first program using IDEA.

  • From the Welcome Screen above click the Create New Project menu.
  • New Project dialog window will be shown. In this dialog you can do:
Create a New Project Window Dialog

Create a New Project Window Dialog

  • Enter the Project Type, choose Java Module.
  • Define the Project Name. We’ll just name it HelloWorld.
  • Choose the Project Location directory.
  • Select the JDK version you’ll be using.
  • Press the Next button followed by the Finish button to continue.

Step 4. IntelliJ IDEA Main Window, creating

  • Here is the Main Window of IntelliJ IDEA.
IntelliJ IDEA Community Edition

IntelliJ IDEA Community Edition

  • The bigger screen shot of the project explorer panel.
Project Explorer Window

Project Explorer Window

  • Before we create a class let’s create a package.
  • Right click the src folder, continued by selecting the New and Package menu.
  • Enter the package name, for instance org.kodejava.introduction
  • To create a class right click on the newly created package, select New and Java Class menu.
  • In the Create New Class dialog enter HelloWorld in the Name text field and choose Class from the Kind drop down selection.
  • Type the following code in the editor.
package org.kodejava.introduction;

public class HelloWorld {
    private String name;

    public String getName() {
        return name;

    public void setName(String name) { = name;

    public static void main(String[] args) {
        HelloWorld hello = new HelloWorld();

        String name = "world";

    private void sayHello() {
        System.out.println("Hello " + getName() + "!");
  • Press Shift + F10 or click the green Run button to execute your code.
  • And we are done!

Other things you can do next is to learn more about the menu and the keyboard shortcuts that you can use while working with the IDE. One good place is to look at the HelpTip of the Day menu. You might also want to read the following cheat sheet from the DZone Refcardz, IntelliJ IDEA Cheat Sheet.

That’s finishes our introduction to the IntelliJ IDEA Community Edition IDE. I hope you can continue your learning and this IDE will surely help you to understand Java better. Because it is not just a tool to write code, it will give you a lot of suggestion so that you can always improve your code quality.