I read this article this morning : Becoming a Better Programmer: A Conversation With Java Champion Heinz Kabutz.
It’s good to see others points of view. It helps open my mind.
Here’s some points that I find interesting:

When I asked Sun’s Brian Goetz the key to writing fast Java code, he said developers should write “dumb code,” by which he meant straightforward, clean code that follows the most obvious object-oriented principles in order to get the best compiler optimization. Compilers are big pattern-matching engines, written by humans who have schedules and time budgets, so they focus their efforts on the most common code patterns, in order to get the most leverage. Goetz argues that clever, hacked-up, bit-banging code will get poorer results.

JSC: What are some of the big mistakes that even experienced Java developers make?

Kabutz: Not unit testing.

To really learn, you need to choose the technology that you want to experiment in and take the time to study and read, which will require sacrificing your personal time. If you follow this advice, you’ll grow more valuable over time and won’t become a computer dinosaur.

If you are currently a Java programmer, you owe it to yourself to experiment in other technologies. Try out Squeak, JRuby, and other languages. Install and use a different IDE. Never stop learning. The moment you stop, you can lose the wave, and it will require a lot of paddling to catch up with it again.