FindBugs looks for bugs in Java programs.  It is based on the concept of bug
patterns.  A bug pattern is a code idiom that is often an error.  Bug patterns
arise for a variety of reasons:

* Difficult language features
* Misunderstood API methods
* Misunderstood invariants when code is modified during maintenance
* Garden variety mistakes: typos, use of the wrong boolean operator

FindBugs uses static analysis to inspect Java bytecode for occurrences of
bug patterns.

WWW: http://findbugs.sourceforge.net/