Garbage Collection?

[Swapnil Trivedi]

11     try{
12         throw NullPointerException()
13        }
14 catch( NullPointerException e){}

Q. How many objects are eligible for Garbage collection after line 13? (Assume there are no dependencies in the above code)

Ans. 0

Why the object created inside the argument of catch block is not eligible for GC?

[Naseem Khan]

throwing does not mean making it for garbage collection.

When exception occurs in try block, then control automatically jump to matching catch statement. In catch, it is going to be referenced by a reference variable e.

Naseem

[Naseem Khan]

See after line 13, there is no object elgible for gc.

I think it sould be better if you say at line 13 not after line 13.

Originally posted by Swapnil:

Why the object created inside the argument of catch block is not eligible for GC?

After the completion of catch block, NullPointerException will be eligible for garbage collection because e is local variable.

[Swapnil Trivedi]

3.  public Integer getNumber(String num){
4.  int i = -1;
5.   Integer number = null;
6.  try{
7        i =Integer.parseInt(num);
8.      }
9.  catch(NumberFormatException ignore){ }
10. number = new Integer(i);
11. return number;
}

How many objects are eligible for GC after execution of line 11?

Hi Naseem: Sorry to bother u..But as long as I understand the answer to this question should be 1. But it's incorrect....the correct answer is 0.
Pls can u explain it....Thanks a ton!!

Regards
Swapnil

[Naseem Khan]

In this case , no. of objects eligible for gc could be 0 or 1 depending upon whether exception occurs at line 7 or not.

If you pass num say "Swapnil", then there will be one object eligible for garbage collection which is NumberFormatException object.

But if you pass num say "1", some String which you can parse then number of object eligible for gc will be zero because there will be no exception in that case.


Regards


Naseem

[Swapnil Trivedi]

Thanks Naseem...


Regards
Swapnil