log4j levels

logLevels.java

log.debug("message"); //Designates fine-grained informational events that are most useful to debug an application.
log.error("message"); //Designates error events that might still allow the application to continue running.
log.fatal("message"); //Designates very severe error events that will presumably lead the application to abort.
log.info("message"); //Designates informational messages that highlight the progress of the application at coarse-grained level.
log.trace("message"); //Designates finer-grained informational events than the DEBUG.
log.warn("message"); //Designates potentially harmful situations.