Which file they go to, depends on your version of Tomcat and how it was installed but the log will always be in TOMCAT-INSTALL/logs.
If you're running Tomcat on Windows and starting from the batch scripts, it may, (again, depending on the version) send the output to the console instead of logging it.
Personally, I stopped using System.out.println a long time ago and went with log4j. Doing so has given me much more control over how logging is performed in both the development and production environments.
Originally posted by Princy Mathew: Those who are seeing the System.out.println output in catalina.out ,can you please tell me which version of tomcat you are using
Why don't you tell us what version you are using. Also tell us how you are starting Tomcat. I'm guessing it's as a Windows service (which usually results in the localhost_log.2007-08-01 files you mentioned earlier).
By the way, the best thing I've ever done, logging wise, is to replace every single System.out.println statement in my app with log4j statements. I now have complete control over where my logging takes place and can tune the logging level while my app is running.
I'll never use System.out.println in a web app again.