java garbage collection and null reference

Question

In my studying for OCJP I came across the following question:

class CardBoard {
           Short story = 200;
           CardBoard go(CardBoard cb) {
                


        

Answer 1

Your CardBoard#go() method does nothing. It receives reference to some object, immediately forgets it, replacing by null, and returns this null value.

So, the line

CardBoard c3 = c1.go(c2);

also does nothing, i.e. no object is created. Just null assigned to c3. So it is not garbage collected because it is already not exist.