Not to be rude, but I don't understand what you are trying to say, and you did not even ask a question.
I guess you're asking how to declare a constant that you can pass between two different classes. In that case,
you should learn about static variables. With a static variable, it is shared between all instances of one class. For example:
if you make let's say five instances of class A, they all share num. Take one of those classes and add... how about 9.
Well num is updated to 9. You could take any instance of that class now, and when you call getNum() it will return 9.
I hope I've been helpful.