FindBugs is a static analyser to find bugs in Java code. There is a FindBugs plugin for Eclipse as well.
It can be downloaded from http://findbugs.sourceforge.net/downloads.html
It can be installed through the Eclipse update manager.
http://findbugs.cs.umd.edu/eclipse update site for official releases http://findbugs.cs.umd.edu/eclipse-candidate update site for candidate releases and official releases http://findbugs.cs.umd.edu/eclipse-daily update site for all releases, including developmental ones