Just reading the comments in a previous post, and realizing how many are truly frustrated trying to get stuff running.  Here's the non-cryptic package manager methodology for a Sun Java install.

1) From the Debian desktop open up the menu - Admin - Synaptic Package Manager

2) Open up the settings tab, and select repositories from the open menu of the Synaptics Package Manager window

3) Add the two links machiner told us about:

3a)  deb http://ftp.us.debian.org/debian lenny main contrib non-free

3b)  deb-src http://ftp.us.debian.org/debian lenny main contrib non-free

4)  Save your repositories lists (close the interface window).  You will get a message that you need to reload, so select the reload icon from the main window.

5)  Clear any messages and then click into the search window, type "Sun java" and then do the search.  Scroll down to the Sun Java 6 Bin file (Binary File) and select it for installation.  Right around it you will see the Sun Java plugin, select it also for installation, apply. 

6)  Close package manager screens

7)  Close and open your Firefox/Iceweasel (all open ones, all desktops, if you are like me!)

8)  Go to a java test page like

http://www.javatester.org/version.html

and verify it's working.  And smile, you haven't lost any hair...

ezsurfer