Java as a security programming language

Hey everyone,
I'm starting a 400 level class next semester and it's going to focus on Java for E-apps. I'm just wondering if Java would be a good language to have under your belt for security programming.

Do many people in the security industry use Java often or do they mostly use C/C++/Perl etc.

Also, any ideas on security apps I could write in Java? Anything useful?

Just curious -

The cool thing about Java applets is that they are executed inside a "sandbox". They are being executed in an entirely blocked off area of memory so they cannot do malicious damage.
At least that's what I remember from my intro Java course (I may be wrong)