jclouds uses Checkstyle to enforce a consistent coding style. Configure your IDE or run mvn checkstyle:checkstyle --quiet -Dcheckstyle.output.file=/dev/stdout -Dcheckstyle.output.format=plain before submitting pull requests.
jclouds Checkstyle does not enforce all coding styles that should be followed in pull requests. However, developers can use this jclouds profile (compatible for import in both Eclipse and Idea): eclipse-code-formatter.xml; Also when using Idea ensure that .* imports are not used (under code style -> imports).
Guava: jclouds extensively uses Guava to provide additional functionality and consistent abstractions as opposed to other libraries, e.g., Apache Commons. That said, Guava usage should be limited in public apis, and not used in domain/value classes. This is to avoid runtime incompatibilities and confusion between types defined in Guava and Java 8.