How do we know which is the right Appender to use between RollingFileAppender and FileAppender?
You may want to read the Apache Log4j 1.2.17 API:
org.apache.log4j.FileAppenderFileAppender appends log events to a file.
org.apache.log4j.RollingFileAppenderRollingFileAppender extends FileAppender to backup the log files when they reach a certain size.
来源：https://stackoverflow.com/questions/25061780/can-log4j-1-2-whats-the-difference-between-rollingfileappender-and-fileappender