(update-)alternatives install java

Here’s the command to install an alternative installation of Java:

alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.6.0_04/bin/java 99

In this case I used the self extracting file (not the RPM) from Sun, and moved the directory to /usr/lib/jvm/jdk1.6.0_04.

Update:
To finish it off, you need to do this:

alternatives --config java

There are 2 programs which provide 'java'.

  Selection    Command
-----------------------------------------------
*+ 1           /usr/lib/jvm/jre-1.4.2-gcj/bin/java
   2           /usr/lib/jvm/jdk1.6.0_04/bin/java

Enter to keep the current selection[+], or type selection number: 2
[root@localhost jvm]# java -version
java version "1.6.0_04"
Java(TM) SE Runtime Environment (build 1.6.0_04-b12)
Java HotSpot(TM) Client VM (build 10.0-b19, mixed mode, sharing)

Sometimes SELinux will prevent something from launching (e.g. Eclipse), and you’ll have to run a command like:

chcon -t textrel_shlib_t /usr/lib/jvm/jdk1.6.0_04/jre/lib/i386/clientlibjvm.so