Before doing such a thing, you should really try to understand the difference between references and objects, and more deeply, the difference between copying a reference vs copying an object.
Product is an object stored in a memory zone called Heap. "tmpRef" is a reference that contains the address that points to that object.
This code:
Product tmp = tmpRef;
does not copy any "Product" objects but it simply assign the tmpReference in a new reference variable called tmp. So, you´ll have 1 Object pointed by 2 references. Passing a reference (4 bytes in a 32bit system) is very cheap. That´s why you can pass objects in your methods as parameters. It´s what it is called "copy by reference".
The final
keyword means that the reference is immutable, not the Product
object.
Probably you have confusion because these logic is not applied to primitive objects, where reference copy does not exist, but primitives are always copied by value, and never by reference.
So if you want to do not change the original object, you do need to create new Product
objects in the heap.
Hope this helps.