What is Sonar
Sonar gauges quality of Java applications through the observance of coding rules conventions, metric measures and advanced indicators.
Sonar contributes to make development more transparent and to keep projects under control. Dashboards offer a global vision to managers and standard open-source components enable proactive control to the developer environment.
Sonar helps development teams to achieve continuous improvement. Have a look at the demo and give it a try at http://sonar.codehaus.org.
Open source components