Write statements in File instead of Tomcat OutPut

How to write statements in file instead of Tomcat Output

import org.apache.log4j.Logger;

import org.apache.log4j.Level;

Logger log = Logger.getLogger("sailpoint.services.bshdemo");

log.debug("hello debug world");

log.info("hello info world");

log.warn("hello warn world");

log.error("hello error world");   

return;