Ubuntu 10.04 (lucid)
Reason install Sun Java instead using OpenJDK:
Some applications have problems with OpenJDK, ie. Freenet, Wuala, Sparnord, but work fine with Sun JRE. A Google search reveals many applications and issues. So if you want to use one of these applications you would better use Sun Java.
1) Click Applications -> Software Centre -> In the Menubar, choose Edit -> Software Sources. Go to tab Other Software and tick the first entry ("http://archive.canonical.com/ubuntu lucid partner"). Close and confirm the "Reload".
2) In Software Centre, search for "sun java" and install the first package ("Sun Java 6.0 Plugin").