String filename = ... // generate name of new logfile
    Logger logger = new MyLogger(filename);
    // do as you need with logger
    ...

log4j.rootLogger=DEBUG, ROOT
log4j.appender.ROOT=... #configure main(root) appender

# configure logger for com.foo.1 category
log4j.logger.com.foo.1=INFO, ONE
log4j.appender.ONE=... #configure appender ONE

# configure logger for com.foo.2 category
log4j.logger.com.foo.2=INFO,

public static String findInList(List<Object> list, Object pattern)
{
    for(Object o : list)
        if(o.equals(pattent)
            return o.toString();

    return null;
}