Loggers should be:

• private: not accessible outside of their parent classes. If another class needs to log something, it should instantiate its own logger.
• static: not dependent on an instance of a class (an object). When logging something, contextual information can of course be provided in the messages but the logger should be created at class level to prevent creating a logger along with each object.
• final: created once and only once per class.

Noncompliant Code Example

With a default regular expression of LOG(?:GER)?:

public Logger logger = LoggerFactory.getLogger(Foo.class);  // Noncompliant

Compliant Solution

private static final Logger LOGGER = LoggerFactory.getLogger(Foo.class);

Exceptions

Variables of type org.apache.maven.plugin.logging.Log are ignored.