Since I upgraded to Mac OS X Tiger, I also installed Java 1.5 on my PowerBook.
Apple provides a small application to change the default JVM to 1.5 instead of the standard 1.4.2. However it is only useful for Applets and WebStart applications.
To change the default JVM for the
$ cd /System/Library/Frameworks/JavaVM.framework/Versions
$ sudo mv Current Current.old
$ sudo ln -s 1.5 Current
Et voila!
$ java -version
java version "1.5.0_02"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_02-56)
Java HotSpot(TM) Client VM (build 1.5.0_02-36, mixed mode, sharing)
