combining codes

I am sure that over time my questions won't be so lame but until then....
I have a small code that I finally made that does simple math (+-*/), but I want to add a snippet that I found and I want to add it to my code. I didn't find it here or in a book (yet) but how does one go about connecting two seperate codes? Maybe I am overthinking this and it's right in front of me.
thanks in advance

...newbie to the JAVA world, be gentle.
I have many questions.

well -- you cut (or copy) the code, then paste it inside you function, and make sure they use the same variables..
you are going to have to be a bit more specific for more help than that.

"There are no facts, only interpretations."
-Friedrich Nietzsche