Thanks for your reply Tim,
and Yes, a few minutes back found the solution for this problem.. I just put this attribute reloadable="true" under tomcat/conf/context.xml
and this solve my problem.. its load the changed .class file without any sweat.
Tomcat6 is infamous for running out of PermGen space when updating,
I agree with statement because i have seen this error during my development.
for that I read somewhere to extend memory of primsize with little text initialization of JAVA_OPTS variable inside catalina.sh under tomcat/bin/
now this got solved and premGen error didn't show up again..