Java developers and testers should use FindBugs to find and fix Java bugs. It’s free, and the FindBugs team has concentrated on having a high hit ratio, as developers won’t use lint’ing tools that spew out pedantic non-errors. FindBugs can run standalone or as an Eclipse plug-in. Watch the Google Labs video linked on the front page for a good 45-minute introduction.
Here are two example bugs from an open-source project I’m interested in.� Click to view.