Installation of Java on Debian 6
Solution 1:
On Debian and Debian-based systems usually /usr/bin/java is just a symlink to /etc/alternatives/java. The reason for this design is that many versions of the same software can coexist together (in your case Java 1.5 and 1.6).
Run:
sudo update-alternatives --config java
to choose default Java version.
For further information on updates-alternatives see:
http://www.debian-administration.org/articles/91