...you might also want to check out the great O'Reilley book "OS X for the Java Geek"-- it's got a funny name, but it really is a great source of information on how Java lives on OS X. I've just scratched the surface of the book and am already quite happy with it.
"Write beautiful code; then profile that beautiful code and make little bits of it uglier but faster." --The JavaPerformanceTuning.com team, Newsletter 039.
Bear is right though, you don't need to explicitly set paths and stuff because it's all done for you. You just need to set your JAVA_HOME variable to /Library/Java/Home for any tools that use it.
BTW, have you tried just typing javac at the command prompt? I don't remember installing the JDK but then again I did install the developer tools package. [ October 07, 2004: Message edited by: Simon Brown ]