created 2006 · complexity basic · author emmby · version 7.0
Jar files are really just zip files, and you can browse them from within Vim simply by treating them the same as Vim treats zip files.
If you want to figure out how to do this yourself, simply read :help new-filetype and zipPlugin.vim in your runtime/plugins directory.
For the impatient, just place the following in a file named ~/.vim/ftdetect/jar.vim (if you're on Unix):
au BufRead,BufNewFile *.jar,*.war,*.ear,*.sar,*.rar set filetype=zip
If you Vim a jar file now, you'll be able to browse it.