Data Jelly

My most recent project involved putting together a client-side tool that would help upload files to my web site. Being a Java developer, I knew it would be very easy to code this with minimal effort needed to support I/O, network, and SSL. However, I wanted to be able to provide my clients with a stand-alone executable.

I'm sure that the best approach would be to develop this tool in another language (such as C/C++), but felt this would be a big learning curve for me. Instead, I quickly searched Google to see if there was a way to compile Java code into a native Windows binary. I found that there are definitely tools out there that can help do this, but it took some time to research and figure out how to get it all working.

So here are the steps I eventually figured out in order to compile Java code into a Windows EXE file:

Step 1
I found this site that provides a pre-compiled version of the GNU Java compiler:
http://www.thisiscool.com/gcc_mingw.htm

I scrolled down to GCC/GCJ 4.02, where it says "The Bundle", and download the .tar (similar to .zip) file. The file was about 64MB. (Note: The file download had a .bz2 file extension, but my browser seemed to automatically rename it to .tar)

Step 2
Extract the .tar file to a directory of your choosing. You should be able to use a tool such as WinZip or 7-Zip to extract .tar files.

Step 3
Open a command prompt window and navigate to the directory where the files are extracted. Go into the "gcc-4.0\bin" directory. Run this command to compile you Java file(s) into an EXE file:

gcj --main=com.package.name.ClassName ClassName1.java ClassName2.java ClassName3.java ...

Note that you will need to use the proper path for each java file you'd like to compile. Also note that you will need to list out each Java file that is a dependency of the main class. I believe you can also set your classpath in an environment variable, but I had some issues doing this because it seems that gcj does not currently support Java 1.5+.

Step 4
This command should generate a file named a.exe, which you can then rename to anything you'd like. You should now be able to execute your Java code as a stand-alone program!

So far, I have only built a simple "Hello World" program to test it out. I'm not too sure how well it will support GUIs (such as Swing), but it seems that it should work pretty well for command-line programs.

Lastly, it's worth mentioning that the .exe file that is generated will be pretty big. The simple "Hello World" program was over 2MB in size. It seems that compiling Java into a native binary will always have a certain amount of overhead, due to the garbage collector and other aspects of management that Java performs for you.