Question on gc

How many objects are avialble for GC

class CardBoard {
Short story = 5;
CardBoard go(CardBoard cb) {
cb = null;
return cb;
public static void main(String[] args) {
CardBoard c1 = new CardBoard();
CardBoard c2 = new CardBoard();
CardBoard c3 = c1.go(c2);
c1 = null;
// do Stuff
}
}

i think 2 cause c1 is null and c3 is being returned as null so remaining two objects are C2 and short but K&B books says following

A. 0
B. 1
C. 2
D. Compilation fails.
E. It is not possible to know.
F. An exception is thrown at runtime.

C is correct. Only one CardBoard object (c1) is eligible, but it has an associated Short
wrapper object that is also eligible.

I mean answer is right but object is different why C1

[ September 30, 2008: Message edited by: mukki pandey ]
[ September 30, 2008: Message edited by: mukki pandey ]

what is the question here?

I cant understand your question.

How many objects are avialble for GC

according to me C2 and short but k&b says C1 and short how C1 is avialable for GC since its already assigned to null

can anyone reply please

Objects created in the example are 4 i.e. one referenced by c1 and short in c1 & the other one by c2 and short in c2.
c3 is just a refernce variable having null value.
As c1 is assigned null value, only the object which is referenced by c1 and short in c1 are eligible for GC. c2 is still referring to the object which was created in line 2. So it is not eligiible for GC.

Remember copy of variable c2 is passed to the method c2!

one thing : you have missed closing brace for the method go()!
[ September 30, 2008: Message edited by: M SRILATHA ]

Also check on the Errata for the book. The Short is created by autoboxing, and based on the value (and due to the cache), it isn't eligible for GC. In the corrected version, the short has a larger value.

Henry

thanks :-) i got it