Installing PMD For Emacs:

1) Download PMD-0.4 from SourceForge, and unpack into a directory.

2) Copy src/elisp/pmd.el to a directory on your Elisp Path

3) Inside your ".emacs" file, (require 'pmd)

4) Set the following variables in ".emacs"
   pmd-java - Java binary to run PMD with.
   pmd-home - Directory where PMD was installed.
   pmd-rulesets - Ruleset to use (must be in the PMD jar.)

There is a customize group under PMD, which you can also
use to customize PMD installation.

Also, I'm sure there are others out there who know more about
customizing Emacs than I do.  Feel free to chip in here and
there.