Assignment question...

[Deepak Bobal]

class cardBoard
{
Short story=5;
cardBoard go(cardBoard cb)
{
cb=null;
return cb;
}
public static void main(String[] arg)
{
cardBoard c1=new cardBoard();
 
cardBoard c2=new cardBoard();
 
cardBoard c3=c1.go(c2);
c1=null; 
System.out.println(c1==null);
System.out.println(c2==null);
System.out.println(c3==null);
}
}
 

this code sample is on page 259 of n B.
****************************
Question is how many objects are eligible for GC after line "c1=null"
Answer is given 2(one is Short story and another is c1)

But according to me there should be 4
two are as the answer is given.
third is "c3" as it is set to null after invoking go() method.
forth is "c2"(not sure) as we are passing it as argument in go()
so in body of method it is being set to null (if i am right?)


**************************************************
What's your opinion???

Thanks
Deepak


[BSouther: Added UBB CODE tags]
[ March 04, 2008: Message edited by: Ben Souther ]

[Ben Souther]

Originally posted by Deepak Bahubal:

this code sample is on page 259 of n B.

When you quote your sources, please don't assume that everyone will know what 'n B' means.

[Deepak Bobal]

Sorry
I missed The letter K.Its K and B.
Kathy Sierra And Bert Bates.

[Rahul Singhai]

Hi Deepak,
There will be only 2 objects eligible for gc() as mentioned in answer.
c2 will not be set to null. because cb(object created in go) is a reference for c2. assigning cb=null dosnt means c2 is assigned to null.
So only c1 and 'Short' object inside it will ne eligible for gc().
Hope it has clear your dounts.

[Deepak Bobal]

But what about c3 that is being set yo null by returning value of go().

[Rahul Singhai]

Deepak,
c3 is never instantiated. it is just a reference variabble, so there is no aboject it is referring to rather it is referring to null value. So there is no point of garbage collection.
Hope it has cleared your query.

[Deepak Bobal]

Yah, Thanks Rahul You simply clears my doubts.

[Nabila Mohammad]

Can some tell me why c2 is not null.
Isnt cb pointing to c2 on the heap.So if cb is null wouldnt that mean, c2 is null as well.
Can some one make this more clear.

[Gaurav Arora]

Originally posted by Nabila Mohammad:
Can some tell me why c2 is not null.
Isnt cb pointing to c2 on the heap.So if cb is null wouldnt that mean, c2 is null as well.
Can some one make this more clear.

The actual object, c2 is not null because the method go only holds a reference to c2 and not the actual object. That reference is null, not the object.

[Nabila Mohammad]

Got it.
Thanks.