This presentation: http://www.cafeaulait.org/slides/eclipseworld2005/staticcode/
PMD: http://pmd.sourceforge.net/
FindBugs: http://findbugs.sourceforge.net/
Checkstyle: http://checkstyle.sourceforge.net/
Java PathFinder: http://ase.arc.nasa.gov/havelund/jpf.html