Tomcat Java Runtime Version java.lang.CharSequence

System

I have built some Java packages for use with ExternalTasks in TeamSite using j2sdk1.4.1_01. Now I would like to use the same classes in front-end stuff. When I try to instantiate these from within a JSP page using the Tomcat that gets installed with TeamSite, I get an error when the packages reference java.lang.Charsequence (used for parsing XML), which was apparently only introduced with 1.4.

What is the best way to get around this? Do I have to install another instance of Tomcat that uses a different Java runtime? Has anyone done this and if so, what are the issues? Or can I change the one that comes with TeamSite to use a different runtime?