[CentOS] Upgrading Java on CentOS 4.5

# rpm -qa | grep -E '^(java|jdk|jre)-'
jre-1.6.0_03-fcs
java-1.4.2-gcj-compat-1.4.2.0-27jpp
jdk-1.6.0_03-fcs

java is a CentOS package.  jdk and jre are from Sun.
(I need Java >= 1.5.0 for an application I'm installing.)

# update-alternatives --config java

There are 1 programs which provide 'java'.

  Selection    Command
-----------------------------------------------
*+ 1           /usr/lib/jvm/jre-1.4.2-gcj/bin/java

But how do I tell my system to use the 1.6.0 version?
Is there a step that I'm missing to finish the upgrading?

Thanks,
Scott