Java Decompiler (jd-gui) is a cute little tool I like using when working in Java. Unfortunately it only comes in 32-bit linux. So if you are on 64-bit linux (considering that everything is going 64-bit except a number of windows apps), you seem a little bit out of luck.
In the past, you would have installed the entire ia32-libs but the new Ubuntu Multi Architecture changes everything a little bit.
So you will have to install the individual 32-bit versions of the dependent libraries to get jd-gui working
sudo aptitude install libgtk2.0-0:i386
sudo aptitude install libcanberra-gtk-module:i386
sudo aptitude install gtk2-engines-murrine:i386
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