To use Java with Tomcat on porsche.cis.udel.edu, you need to be using the correct version of the JDK, and have your environment variables set up properly. Here's what you need to do.
Check the environment variable JAVA_HOME by doing:
echo $JAVA_HOME
If you used JAVA in a course previously, you may have this already set. Either way, it needs to be set to:
/usr/local/jdk1.5.0
In addition, you need to have the following directory in your path:
$JAVA_HOME/bin
If you aren't sure how to go about all that, look back at what you did to make everything work on strauss. Know, however, that on porsche, you will NOT put things in a file called .localenv—that's a "strauss" thing. Instead, if you are a csh or tcsh shell user, you'll put those commands in a file called .cshrc, and if you are a bash shell user, you'll put (slightly different) commands in a file called .bash_profile or .bashrc