method returns what happens to garbage collection

[naveen yadav]

Following code is from OCP Practice Exam book. It says

class Account { Long acctNum, password; }
5. public class Banker {
6. public static void main(String[] args) {
7. new Banker().go();//===================Object created: count 1
// do more stuff
9. }
10. void go() {
11. Account a1 = new Account();//===============Object created :count 2
12. a1.acctNum = new Long("1024");//===============Object created :count 3
13. Account a2 = a1;
14. Account a3 = a2;
15. a3.password = a1.acctNum.longValue();
16. a2.password = 4455L;//===============Object created :count 4
17. } }

D. Four objects are eligible for garbage collection.



How the answer is changed in folowing case

Banker ob = new Banker();
ob.go

[dennis deems]

Not all of us carry our K&B books around all day. ;) So give us the full question please. Then, tell us what YOU think will happen if the code is changed as you suggest.

[Jeffrey Tian]

I has doubt on this question:

On Line 15. a3.password = a1.acctNum.longValue();
an object is created. The total number of objects should be 5. Am I right?

[naveen yadav]

Here is Complete question :

28. Given:
4. class Account { Long acctNum, password; }
5. public class Banker {
6. public static void main(String[] args) {
7. new Banker().go();
8. // do more stuff
9. }
10. void go() {
11. Account a1 = new Account();
12. a1.acctNum = new Long("1024");
13. Account a2 = a1;
14. Account a3 = a2;
15. a3.password = a1.acctNum.longValue();
16. a2.password = 4455L;
17. } }

When line 8 is reached, which are true? (Choose all that apply.)
A. a1.acctNum == a3.password
B. a1.password == a2.password
C. Three objects are eligible for garbage collection.
D. Four objects are eligible for garbage collection.
E. Six objects are eligible for garbage collection.
F. Less than three objects are eligible for garbage collection.
G. More than six objects are eligible for garbage collection.

Correct Ans : D


Now follow :
As if change is made in Banker class

Banker ob = new Banker();
ob.go

As with my understanding None of the object is eligible for GC since ob still hold the reference to the object(s).

[Jeffrey Tian]

Looks like all of us didn't Google this questions. This question has been discussed a lot in this forum. Click Here

I have another concern on answer B. The book says: B is correct, although when line 8 is reached, the references are lost.
Both references have gone, how can we compare them?