Log4j is provided with different logging levels:
It is useful for debugging application. It should not be used in production environment.
It can be used to display information messages in logs. It is one level higher than DEBUG.
It can be used to provide warning about an unexpected event.
It is generally used in production environment and used to provide information about any kind of exception or error. It is one level higher than WARN.
It can be used for condition which causes application to halt. We generally do not use this logger level.
It is used to turn on all levels of logging. Once this is configured and the levels are not considered.
It is opposite to ALL level. It turns off all the logging.
It gives more detailed information than the DEBUG level and sits top of the hierarchy.
Table with log levels: