I prefer sun-java6-jdk ..
A manual method for the install :
http://ubuntuforums.org/showthread.php?t=1460594
..... Some packages depend on 'sun-java6-jdk' ?
Also see post #10, please. ........
.. Or add some "karmic" lines to /etc/apt/sources.list , to use
sudo apt-get update && sudo apt-get install sun-java6-jdk ..
(Please use the url, you have for lucid.)
My example, the Danish url :
deb
http://dk.archive.ubuntu.com/ubuntu/ karmic universe
deb
http://dk.archive.ubuntu.com/ubuntu/ karmic-updates universe
deb
http://dk.archive.ubuntu.com/ubuntu/ karmic multiverse
deb
http://dk.archive.ubuntu.com/ubuntu/ karmic-updates multiverse
sudo update-alternatives --config java
.. is required if you have other 'java' installed.
..