Perfect, you have our permission, go ahead.
Since you didn't ask any question, it is difficult to give you a better answer.
I strongly recommend you to read:
How to ask a question[
^] and
What have you tried?[
^]
You can have a look to other ready whiteboards in the net and see how they work, then start your own.
i.e:
http://sourceforge.net/projects/javawhiteboard/[
^]