Core Duo MacBooks (as opposed to Core 2 Duo) are 32-bit rather than 64-bit, and Apple only provides Java up to version 1.5 for 32-bit machines. Update: the upgrade to Snow Leopard includes an official 32-bit version of Java 1.6.
Installing SoyLatte - a port of Java 1.6 to OS X - is quite straightforward:
- Download the binary 32-bit OpenJDK6 for Mac OS X (currently openjdk6-b16-24_apr_2009-r1.tar.bz2) and extract it to /usr/local/soylatte.
- export JAVA_HOME=/usr/local/soylatte
- export PATH=/usr/local/soylatte/bin:$PATH
Extensions (JAR files that would normally go in /Library/Java/Extensions) go in /usr/local/soylatte/jre/lib/ext.
'Endorsed' libraries go in /usr/local/soylatte/jre/lib/ext/endorsed.
I haven't yet found a way to get SoyLatte to show up in the "Java Preferences" app, which is needed in order to make Java 1.6 available to other applications like OpenOffice; symlinking /System/Library/Frameworks/JavaVM.framework/Versions/1.6.0/Home to /usr/local/soylatte doesn't seem to be enough.