A tool for static analysis to look for bugs in Java code
SpotBugs is a program that uses static analysis to look for bugs in Java code. It is free software, distributed under the terms of the GNU Lesser General Public License. SpotBugs is a fork of FindBugs (which is now an abandoned project), carrying on from the point where it left off with the support of its community. Please check the official manual for details.
Checkstyle is a development tool to help programmers write Java code that adheres to a coding standard. By default it supports the Google Java Style Guide and Sun Code Conventions, but is highly configurable. It can be invoked with an ANT task and a command line program.