Then go for it
Just download the appropriate JDK from Sun and install it.
It comes as a .bin file. You just have to chmod +x <filename> it. Run it and accept the license agreement. It will extract the embedded rpm for you in the same directory. Then just run, as root, "rpm -Uvh <filename>.
That's it other than setting up the $JAVA_HOME and appending the java directory to your path. This can be accomplished by adding the following lines to your /etc/profile or $HOME/.bashrc file. You may have to change the "j2sdk1.4.2" depending on what JDK version you installed.