Set log rollback for log4j

Every time I see a log file on the server, a file is generated every 100MB: I have never understood why some logs will append a timestamp or number to the back of the log after a period of time. It turns out that there is a configuration in log4j - log rollback . 
The specific use method is as follows

log4j.rootLogger=DEBUG,ROLLING_FILE,stdout
log4j.appender.stdout=org.apache.log4j.ConsoleAppender    
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout    
log4j.appender.stdout.layout.ConversionPattern=%d-5p %c{1} %x - %m%n
#Set file rollback
log4j.appender.ROLLING_FILE=org.apache.log4j.RollingFileAppender
log4j.appender.ROLLING_FILE.File=./log/test.log
log4j.appender.ROLLING_FILE.Append=true
#Set the size of each log file to 3KB, which is convenient for testing
log4j.appender.ROLLING_FILE.MaxFileSize=3KB
#Set the maximum number of log files to 3
log4j.appender.ROLLING_FILE.MaxBackupIndex=3
log4j.appender.ROLLING_FILE.layout=org.apache.log4j.PatternLayout
log4j.appender.ROLLING_FILE.layout.ConversionPattern=<%d>[%5p] %c-%L -%m%n

 1) Test procedure:

public class TestLog {
	public static final Logger log = LoggerFactory.getLogger(TestLog.class);
	public static void main(String[] args) {
		int count = 0;
		while(true){
			count++;
			log.debug("count=" + count);
			if(count % 30 == 0)
				break;
		}
	}
}

 Log output result:

 2) Modify the code:

if(count % 100 == 0)
				break;

 Log output result:

 

 

3) Modify the code so that the generated log files exceed the set maximum number of 3

if(count % 200 == 0)
				break;

 output log result

 

 

 

 I believe that through the comparison of the above three results, it is easy to understand what is going on with the log rollback!