i am middle building guijava stack i would know if how do i

I am in middle of building a GUI(Java) for a stack. I would like to know if how do I keep the numbers in the stack so it will be calculated. For ex: lets say I push 1 then 2 then I add them I get 3. Now i would like to push 4 and then add that so I get 7.
 
Do you need a similar assignment done for you from scratch? We have qualified writers to help you. We assure you an A+ quality paper that is free from plagiarism. Order now for an Amazing Discount!
Use Discount Code "Newclient" for a 15% Discount!

NB: We do not resell papers. Upon ordering, we do an original paper exclusively for you.