🚀 go-pugleaf

I got an assignment which will be due next week, which require encryption
service at the server side using JAVA code.  I am not sure how to implement
such an encryption, is there any method I can use or should import some
special class or ...?  I am confused.

The requirement follows:
"The server implements a simple Caesar-like cipher (an example of which is
given in Tannenbaum, 3rd Edition, p582) on the usual set of alphabet and
punctuation characters. All characters in this set are encoded by shifting
their position by thirteen places -- hence this cipher is popularly called
"rot13". Control characters need to be handled carefully, but (as a general
rule) are not encoded and may be discarded by the client or server. Once
again, some care needs to be taken in defining which characters can be
removed and which cannot."
more detail can be found at
http://www.cse.unsw.edu.au/~cs9331/Assignments/project.html.

Any advice on how to implement this most appreciated.