Why am I not able to install libgcj6?

[Josef Lowder]

.
This replaces the previous message that had a confusing typo: 

KevinO wrote: 
> This information may only apply to cooker, not the stable distribution.
> Try going to the 'easy Urpmi' website and setting up sources for main, 
> contrib, etc. ( Remove any invalid sources first -> urpmi.removemedia -a )
> http://easyurpmi.zarb.org/

Then tickticker wrote:
> you need to be sure your sources are good, perhaps it's in the 
> Cooker repository, not base, or heaven forbid PLF (penguin 
> liberation front).
> 
> also, libgcj.so.6 is different than libgcj6, you may be trying to 
> install the wrong dependency... Welcome to dependency hell, let me 
> be the first to welcome you!
> 
> check your sources, and if you don't know if you are current, use 
> http://easyurpmi.zarb.org/ to reset them as the previous poster said.

Sorry I'm so dense, but I'm really in a fog about what to do here. 
>From the above comments, is this the actual command I need to use: 
   # urpmi.removemedia -a

I have not yet run the above command, but I went to the easyurpmi.zarb.org
website to see what was there, but could not understand what to do there or
how to do it.  I saw" "proceed to step two" and a check box for this: 
"Show specific sources too" --- but how am I supposed to know what sources to
choose?