For example, the first time I run an application (or immediately after I clear out the /logs directory), I want log4j to write the application\'s logs to a file called log.0
Solution with log4j2:
%level\t%d{yyyy-MM-dd HH:mm:ss} %c: %m%n
Note OnStartupTriggeringPolicy and %i in filePattern. This way, Log4j will create new log file with index each time you run App.