Does two languages use the same stack and heap on the ram?
Two different programs never use the same heap. They each, get a portion of virtual address space, that can overlap in numbers somehow, but these are independent. When a program actually needs pages to be in RAM - it allocates them, in a lazy fashion, usually by 4KB ( might be bigger ). This is done via a Page Table, which is able to map virtual address space to phisycal one ( potentially swap too ). 
You probably need to understand that you do not require everything, all the time in RAM. Your code can do a little portion, then give that space in RAM to someone else, or even swap out.
I was reading regarding the memory allocation in python and was wondering if I have java and python installed in the same computer system then does java and python use the same stack and heap or they have different stack and heaps allocated for them in the RAM? 
Can anyone please help me to clear my doubt.
Thanks in Advance.