I often find it difficult to feign interest the discussion of Java in the post Sun Microsystems era. Don't get me wrong, I get that there's a lot of Java out there, I get that there are a number of technological strengths and advantages that Java has in contrast some other programming platforms. Consider my post about worfism and computer programing for some background on my interest in programing languages and their use.
I apologize if this post is more in the vein of "a number of raw thoughts," rather than an actual organized essay.
In Favor of Java
Java has a lot of things going for it: it's very fast, it runs code in a VM that lets the code execute in a mostly isolated environment which increases reliability and security of the applications that run on the Java Platform. I think of these as "hard features" or technological realities that are presently implemented and available for users.
There are also a number of "soft features," that Java has that inspire people to use it: an extensive and reliable standard library, a large expanse of additional library support for most things, a huge developer community, and it has inclusion in computer science curricula so people are familiar with it. While each of these aspects are relatively minor, and could theoretically apply to a number of different languages and development platforms, they represent a major rationale for it's continued use.
One of the core selling points of Java has long been the fact that because Java runs on a virtual machine that can abstract differences between different operating systems and architectures, it's possible to write and compile code once and then run that "binary" on a number of different machines. The buzzword/slogan for this is "write once, run anywhere." This doesn't fit easily into the hard/soft feature dichotomy I set up above, but it nevertheless and important factor.
Teasing out the history of programing language development is probably a better project for another post (or career?), but while Java might have once had a greater set of support for many common programming tasks, I'm not sure that it's sizable standard library and common tooling continues to overwhelm it's peers. At best this is a draw with languages like Perl and Python, but more likely the fact that the JDK is so huge and varied increases incompatibility potentials. And needing to download the whole JDK to run even minimalist Java programs. Other languages have addressed the tooling and library support in different way, and I think the real answer to this problem is write with an eye towards minimalism and make sure that there are really good build systems.
Most of the arguments in favor of Java revolve around the strengths of the Java Virtual Machine, which is the substrate where Java programs run. And it is undeniable that the JVM is an incredibly valuable platform, and every report that I've seen concludes that the JVM is really fast, and the VM model does provide a number of persuasive features (e.g. sandboxing, increased portability, performance gains.) That's cool, but I'm not sure that any of these "hard" features matter these days:
Most programing languages use a VM architecture these days. Raw speed, of the sort that Java has, is less useful than powerful concurrent programing abilities and is offset by the fact that computers themselves are absurdly fast. It's not to say that Java fails because others have been able to replicate the strengths of the Java platform, but it does fail to inspire excitement.
The worth of Java's "cross platform" capabilities are probably negated by service-based computing (the "cloud,") and the fact that cross platform applications, GUI or otherwise, are probably an ill gotten dream anyway.
The more I construct these arguments, I keep circling around the idea that while Java pushed a lot of programmers and language designers to think about what kind of features that programing languages needed. The world of computing and programming has changed in a number of significant ways, and we've learned a lot about the art of designing programming languages in the mean time. I wonder if my lack of enthusiasm (and yours as well, if I may be so bold) has more to do with a set of assumptions about the way programing languages should be that haven't aged particularly well. Which isn't to say that Java isn't useful, or that it is no longer important, merely that it's become uninteresting.