1) Install latest JDK

Download and run the "Java SE Development Kit" installer for Mac OS X x64:

https://jdk.java.net

2) Launch Unix terminal

Using Finder go into "Applications" and then open the "Utilities" folder.  Open Terminal and you're now at the Unix prompt.  Enter the following command to verify Java is installed:

      java -version
   

3) Make project folder

Enter these two commands:

      mkdir showtime
      cd showtime
   

The first command creates a folder called "showtime", and the second command moves you into the new folder.

4) Write some Java code

Get the sample Java code and take a look at the Swing commands that create a simple window for displaying the current time:

      curl --remote-name https://centerkey.com/mac/java/ShowTime.java
      cat ShowTime.java
   

You'll see the code:

         import java.util.Date;
         import javax.swing.*;

         public class ShowTime {

            public static void main(String[] args) {
               JFrame frame = new JFrame();
               frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
               frame.setTitle("It's Showtime!");
               frame.getContentPane().add(new JLabel(new Date().toString()));
               frame.pack();
               frame.setVisible(true);
               }

         }
      

5) Compile Java program

Back at the Unix prompt, compile the Java program into a class file:

      javac ShowTime.java
      ls -l
   

It is possible to run the class file directly, but that results in a poor user experience.  Instead we will create a more convenient executable JAR file.

6) Make executable JAR

Before we make an executable JAR file, we need a manifest file to indicate which class contains the "main" function.  Create the file:

      echo "Main-Class: ShowTime" > MainClass.txt
      cat MainClass.txt
   

The resulting manifest file contains a single line:

         Main-Class: ShowTime
      

Now use the following jar command to create the "ShowTime.jar" file:

      jar cmf MainClass.txt ShowTime.jar *.class
      ls -l
   

Test your executable JAR with the following command:

      java -jar ShowTime.jar
   

The "It's Showtime!" window with the current time should display in the upper left corner of the screen.  Click the red button (marble) to exit the program.

Note: While the manual commands above for steps #5 and #6 work fine, you could automate them using Ant with a build.xml file.

7) Create application icon

The default icon for an executable JAR is a coffee cup.  To add a custom icon, we need to create an .icns file.

Use the following commands to download a sample PNG image, resize the image to appropriate dimensions for an icon, and convert it into the .icns format:

      curl --remote-name https://centerkey.com/mac/java/ShowTime.png
      mkdir ShowTime.iconset
      sips -z 128 128 ShowTime.png --out ShowTime.iconset/icon_128x128.png
      iconutil --convert icns ShowTime.iconset
      ls -l
   

8) Build Mac OS X application with installer

The following commands move the icon file into the package folder and then use the javapackager tool to build the ShowTime.app appplication and wrap it in into an installer:

      mkdir -p package/macosx
      cp ShowTime.icns package/macosx
      jdk=$(/usr/libexec/java_home)
      $jdk/bin/javapackager -version
      $jdk/bin/javapackager -deploy -native dmg \
         -srcfiles ShowTime.jar -appclass ShowTime -name ShowTime \
         -outdir deploy -outfile ShowTime -v
      cp deploy/bundles/ShowTime-1.0.dmg show-time-installer.dmg
      ls -l
   

Note 1:

The javapackager tool is the way forward while the legacy JarBundler and AppBundler approaches are now obsolete.

Note 2:

The executable JAR file ShowTime.jar checks in at a mere 0.001 MB, but the installer file show-time-installer.dmg is a whopping 66 MB.  The reason is that it bundles the JRE (an Apple requirement for publishing Java programs to the Mac OS X AppStore).

Note 3:

When you are ready to distribute to the public, you'll want to sign your application with a Developer ID certificate.  Use the productsign tool to apply a certificate.

9) Try it out

Run the installer:

      open show-time-installer.dmg
   

After completing the installation, go into the "Applications" folder and open the "ShowTime" application.  Be sure to check out the "About ShowTime" option on the "ShowTime" menu.

Wrap-Up

For an example of how you might distribute your installer, take a look at:

Snap Backup

That's it.