How to install a specific JDK on Mac OS X?
In a comment under @Thilo's answer, @mobibob asked how to set JAVA_HOME in your .bash_profile on a Mac. Answer:
export JAVA_HOME=`/usr/libexec/java_home` This will dynamically assign to JAVA_HOME the location of the first JDK listed in the "General" tab of "Java Preferences" utility.
See Apple Technical Q&A 1170: https://developer.apple.com/library/content/qa/qa1170/_index.html
EDIT:
If you prefer parentheses to backticks for command substitution, this also works:
export JAVA_HOME=$(/usr/libexec/java_home)
As the message says, you have to go to Apple, not Sun, for Java on the Mac. As far as I know, Apple JDK 6 is installed by default on Mac OS X 10.6 (Snow Leopard). Maybe you need to install the developer tools from your Mac OS X installation DVD (the dev tools are an optional install from the OS DVD).
See: http://developer.apple.com/java/
NOTE This answer from 16 Oct 2009 is now outdated; you can get the JDK for Mac OS X from the regular JDK download page on Oracle's website now.
For people using any LION OS X 10.7.X
They uploaded Java SE 6 version 1.6.0_26 available here