When Microsoft first introduced the .NET platform and its flagship programming language C#, I, like many Java developers, looked at it and said “They’re just copying Java”. Why would I want to develop on the .NET platform which is targeted exclusively at Windows, when I could use the more established Java language and deploy across all platforms including Mac and Linux?

When I heard rumblings of the open source version of .NET, called Mono being developed, I was curious but ultimately wrote it off as it was likely that, since .NET was married to Windows in so many ways, probably most of the libraries for .NET would be platform specific and wouldn’t run properly on Mono anyways.

The past 10 years have seen many new trends come and go, and quite a few shifts in mindshare between the different technologies. One stream of trends that I have been quite interested in as a Java developer and a Mac user, is the role of Java on the Mac.

When Apple first unveiled OS X, Java was at the center of it. They promoted Mac as an excellent platform for Java developers to deploy their programs. They pledged to provide a Mac-specific implementation of Java that would blend into the OS and work seamlessly with the slick new look and feel of Mac. Two key pieces of this puzzle were the Swing Aqua look and feel and the Java Cocoa Bindings. The Swing Aqua look and feel allowed all Swing (the default java UI toolkit) programs to look like native programs on the mac. The Java Cocoa bindings allowed even deeper integration by allowing Java programs to use the native Objective-C classes and widgets directly.

Fast forward to 2011. If you try a google search for Desktop Java on the Mac or related terms you’ll notice that there are lots of articles, tutorials, and documents from the period ranging from 1997 to 2005. But very little after that. This is due to a number of trends and developments during that timespan. Some of these include:

1. Apple deprecating the Cocoa Java bridge. (Turns out that is wasn’t used very much anyways because Java developers could achieve an almost native look and feel using Swing and keep cross-platform compability).
2. Java mindshare had moved predominantly to server-side technologies.
3. The emergence of higher-productivity interpreted dynamic languages like Ruby and Python had stolen a lot of mindshare on the desktop.
4. Objective-C through the introduction of the iPhone and iPod had drastically increased in mindshare – so more developers were familiar with the native tools and would forego trying to work with a language such as java for native applications.
5. Sun seemed to be confused as to which direction it wanted to go – and years of progress were lost (* more on this later).

Nonetheless, during the period of 2005 to present, there have still been some good options for producing high quality desktop applications for the mac. After all it was the only OS with a large user base that shipped with Java. This meant that you could develop for Java and be certain that the target users would be able to use your software without having to download anything extra. Swing still has the Aqua look and feel, and all of those tools and widgets that were developed pre-2005 still worked nicely (except of course those tools that were built upon the Cocoa-Java bridge).

Unfortunately the writing was on the wall and Apple made it official in October 2010 when it announced that it would be deprecating Java on the mac and that future versions of the operating system would not ship with it. It would be up to the open source community and Java’s owner Oracle to provide a Java for the future of the Mac (and this future is still very much unfolding as I type).

So now, at a time when the future of Java on the Mac is as bleak as ever, an unlikely ally enters the fray: .NET – or rather its open source twin, Mono.

Mono has quietly been picking up a following over the past 10 years. It reached 1.0 status in 2004, and has facilitated the development of 2 separate projects, which, together appear to offer the best hope for the future of Java on the Mac:

1. IKVM.NET – A Java virtual machine that runs on .NET and Mono. This tool is able to run Java byte code in Mono and use java libraries natively. It also includes tools to statically compile java as a .NET executable which can be used in .NET or Mono applications. This has opened many doors to both C# and Java allowing libraries developed with java to be quickly compiled a distributed for .NET (e.g. Apache’s PDFBox which is developed in Java but available for both .NET and Java).

2. The Mono Mac project – An objective C binding that allows C# code to directly access the Mac Cocoa classes. The current versions of MonoDevelop (the Open Source Mono IDE) work seamlessly with Apple’s developer tools, especially interface builder so that developing and deploying an application for the Mac using C# is a first class experience.

These two projects together open up a myriad of possibilities for Java on the mac that haven’t been available since the deprecation of the Cocoa-Java bridge. If you have a large existing source base of java code and libraries, you can quite easily now compile them into a Mono library that can be used in a Mono Mac application – and then deploy it natively on the Mac and even distribute your applications in the Mac App store.

And this is how a Windows-Only competitor of Java has evolved into an unlikely ally in staying relevent on the Mac platform.