Can I use part of Processing source code in my code?

Oh. I guess I will use these instead.
But, I have 2 questions now:
What do I do if I will suddenly have a need for some other function in Processing, or someone else’s project under same/similar license, with same conditions? What should I do then?

And, why Processing code reinvents those functions if they are in Java already? Is it faster that way? And if so, then, well, I want those faster functions, and the problem is still there! :v