A FindBugs developer uses the FindBugs software, a program that uses static analysis to look for bugs in Java code. They examine the results generated by the tool, which identifies potential software bugs, including null pointer dereferences, infinite recursive loops, and other runtime errors. The developer then corrects these bugs to improve software quality. They might also customize the tool to check for specific issues relevant to their project or organization. Furthermore, they may contribute to improving the FindBugs tool itself by developing new features or fixing existing issues, all aimed at enhancing software reliability and efficiency.