The Coder's Handbook



What's a Jar?

A jar is simply a Java ARchive file. It's basically a zip file that contains a bunch of Java program stuff. But there are special ones that can be easily run with a simple click.

Runnable Jar

To make a program you can share easily with people who have Java installed on their machine, but might not have access to your code or Eclipse, you can export to something called a Runnable Jar.


  1. Select your project in the Package Explorer and Choose Export

  2. Under export, choose Java --> Runnable Jar File

  3. Make sure your correct project is chosen under Launch Configuration

  4. Use Browse to choose an Export Destination. Give it a name and location that you'll remember.

    • Note: This isn't your final version, so make it something simple you should use a different name from what you want your actual final program to be called.


It's okay if your project compiles with warnings. This just means that one or more of your files has a warning. Most commonly this is just an unused variable or import.


Click here to download a copy of Jarsplice and Portable Java Launcher

Using Slick2D means we need extra stuff

Slick 2D includes files that lets your computer interact with Open GL and the operating system, which is what helps it run fast. These files are called natives. We'll need to use a program called Jarsplice to combine our Runnable Jar with the natives to make something called a Fat Jar which contains everything we need.

Extra Step @ School

So to run a jar file, you will need to have Java installed on the machine. However, BCPS has decided to not allow us to have Java on our computers. Madness. This means we'll have to use an extra program just to open Jarsplice and our final products.

The file above contained Portable Java Launcher. You simply click on that executable then use it to find Jarsplice and load it up. You should see a program that looks like the screenshot on the right.


#1 Adding Jars

  • Click on 1) Add Jars

  • Click on Add Jar(s)

  • Find the Runnable Jar File you just created

#2 Adding Natives

  • Click on 1) Add Natives

  • Click on Add Natives(s)

  • Find the Natives from your project folder (under libs). Add all of them.


#3 - Main Class

  • Click on 3) Main Class

  • Type in the location of your main class. This is the file which has the main method in it. Not the path, just the package and name.

#4 - Create Fat Jar

  • Make a folder to contain your project. This is what you'll eventually submit your running project in. It should have your project name.

  • For example, if your game is named Gecko you can call this "Gecko Runnable"

  • Click on 4) Fat Jar

  • Choose Create Fat Jar


All the Resources

  • Your project almost certainly has a number of supporting files:

    • Images

    • Music

    • Map Files

    • Save Files

  • You'll need to copy all of those from Eclipse and put them in the folder in the same directory structure.

  • Most projects keep their media in a "res" folder.

  • You can literally copy-paste this from Eclipse to Windows.


In eclipse, your media files are not case sensitive. Once you make it a jar, they will be. If you've been careless with file capitalization and the program crashes, you'll need to check every media file and start over.


At Home or on a Personal PC

Click on the Jar and it'll run like an executable.

At School or on a BCPS Laptop

Open Up the Portable Java Launcher and find the file to run it.