As detailed in this great DZone article by Zviki Cohen, Snow Leopard only ships with a 64-bit version of Java 6. In fact, if you upgrade from Leopard to Snow Leopard, the installer will actually uninstall Java 5 and replace it with symbolic links to Java 6.
This proved to by a challenge for my Eclipse needs as 1) you need to make a decision about which flavor (32 bit or 64 bit; Carbon or Cocoa) of Eclipse to install on the Mac, and 2) Eclipse gets confused by the symbolic link to Java 5 and thinks you really do have a real Java 5 JDK installed.
After reading the Dzone article, I decided to go with the 64-bit Cocoa version as that seems in line with where Java and Mac OS are going. Also, as I was going through my installation Eclipse Galileo SR 1 (3.5 SR 1) shipped which provided 64-bit Cocoa versions for all Eclipse profiles (JEE, Java, etc.). The SR 1 release eliminated many of the hoops Zviki talks about in this article, making it a much easier path to choose. After using this version of Eclipse for about a week, I'd say I don't notice a big difference from the 32-bit version, but it certainly seems stable and having it do builds with really big projects (ServiceMix) it seems relatively fast. I do notice my Laptop fan turning on and both cores maxed out, which overall I assume is a good thing as that means that its taking full advantage of my computer during a large complex build...
The next big task was fixing the Java 5 issue. This was an especial challenge / need for me since 1) most FUSE projects still support Java 5 and 2) m2eclipse (Apache Maven support in Eclipse) gets confused importing Maven projects that use Java 5 with Eclipse thinking its got a JDK 5 installed but really its Java 6 (see above note about Snow Leopard linking JDK 5 dir to JDK 6). This post at OneSwarm details how to hack a real JDK 5 onto your Snow Leopard OS. The highlight being
In the terminal:
Get the java 5 that was included in 10.5 "leopard" and unpack
cd /tmp/ wget http://www.cs.washington.edu/homes/isdal/snow_leopard_workaround/java.1.5.0-leopard.tar.gz tar -xvzf java.1.5.0-leopard.tar.gzMove it to your System java folder (password needed)
sudo mv 1.5.0 /System/Library/Frameworks/JavaVM.framework/Versions/1.5.0-leopard
Tell OS X that java 5 actually is java 5
cd /System/Library/Frameworks/JavaVM.framework/Versions/ sudo rm 1.5.0 sudo ln -s 1.5.0-leopard 1.5.0
I also updated the /System/Library/Frameworks/JavaVM.framework/Versions/1.5 link to point to the 1.5.0 link for completeness.
After doing this I updated Eclipse to use the real JDK 5, and m2eclipse with my ServiceMix project built much better. Now I can do both Java 5 and 6 development on 64-bit Cocoa version of Eclipse - all nice and shiny new :-)
Now onto some real coding... :-)