Udo's Techblog

OK, this one might also be widely known but it cost me a few minutes to figure it out, so here it goes: Software Update installs Java 1.6 on 64bit-capable Macs running Leopard. However, this doesn't mean they change the default runtime version that gets called when you click on a jar file or call code directly from the command line.

OS X's Java binaries live in a directory called "/System/Library/Frameworks/JavaVM.framework/Versions". On a 64bit Mac this should contain quite a handful of different runtimes:

lrwxr-xr-x  1 root  wheel    5 Apr 30 12:25 1.3 -> 1.3.1
drwxr-xr-x  3 root  wheel  102 Sep 29  2007 1.3.1
lrwxr-xr-x  1 root  wheel    5 Jan 22 14:00 1.4 -> 1.4.2
lrwxr-xr-x  1 root  wheel    3 Apr 30 12:25 1.4.1 -> 1.4
drwxr-xr-x  8 root  wheel  272 Jan 22 14:00 1.4.2
lrwxr-xr-x  1 root  wheel    5 Jan 22 14:00 1.5 -> 1.5.0
drwxr-xr-x  8 root  wheel  272 Jan 22 14:00 1.5.0
lrwxr-xr-x  1 root  wheel    5 Apr 30 12:25 1.6 -> 1.6.0
drwxr-xr-x  8 root  wheel  272 Apr 30 12:25 1.6.0

This directory also houses two symlinks called "Current" and "CurrentJDK". As root in Terminal, remove those and replace them with symlinks to the 1.6 runtime:

rm Current*
ln -s 1.6.0/ Current
ln -s 1.6.0/ CurrentJDK

There, all done! From now on "java -version" should return something like:

java version "1.6.0_05"
Java(TM) SE Runtime Environment (build 1.6.0_05-b13-120)
Java HotSpot(TM) 64-Bit Server VM (build 1.6.0_05-b13-52, mixed mode)