I once helped write a systems monitoring app for a telecom once -- internship project, but it was well coded. I came back to work some over Christmas, and they ported it to Perl to reduce server load -- it now was written in 10x less code, ran 10x faster, and consumed 10x less RAM. That's all I'm going to say. At the time I was indoctrinated to be very-pro-Java and it really was enlightening. I knew Perl at the time, but how could those few lines of code replace what took me so long to implement?

That, and Java for me is a pain-in-the-you-know-what to manage. Inconsistant API's, bad layout managers, the joke that is "write once run anywhere", bad File I/O, poor OS interlocks, JNI's a pain in the butt, ugly bloated regex syntax (if you aren't locked into 1.3 like we are for SCO (ack) support), slow development speed even among "expert" Java programmers, cultural requirement to use getters/setters versus "real" OO, JVM bugs, etc, etc, etc...really I'm not going to post too much more on the subject since it's just going to get me worked up about how much I hate to use this language everyday at work, and how we should really be using Perl!

Ok, I will add one more thing. For a guy that hasn't written any Java, this article is dead-on IMHO. And I've written a ton of Java:

Paul Graham on Java