Do Exceptions thrown are eligible for Garbage Collection?

[Javier Sanchez Cerrillo]

Here is a bit confusing question for me (Whizlabs SCJP 5.0 - Final Exam - Question 63):

How many objects will be eligible for garbage collection after the execution of line 11 in the following code snippet?

1. public Integer getNumber(String num)
2. {
3. int i = -1;
4. Integer number = null;
5.
6. try{
7. i = Integer.parseInt(num);
8. }
9. catch(NumberFormatException ignore){}
10. number = new Integer(i);
11. return number;
12. }


Possible answers: (choose 1)

A.- 1
B.- 0
C.- 2
D.- 3

-----------------------------------------------------
By the time I tried to solved this question. I chose A (1 object) I did know primitive local variables are created in the stack, so they are not eligible for Garbage Collection, but I looked for the exception thrown.

Are exceptions thrown eligible for Garbage Collection?. They are Objects and they use constructors so they live in the heap.

I would apreciate any help.

[Sanjeev Singh]

Javier,

I did know primitive local variables are created in the stack, so they are not eligible for Garbage Collection

Only objects are eligible for the garbage collection(GC).

In the problem above(after line 8)

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

Objects created
at line 7.
at line 6.
Since the method returns the reference to the object created at line 7 so object created at line 7 will not be GCed.
The NumberFormatException created at line 6 will be GCed as the reference to the object will be destroyed after line 6.
So only one object will be GCed and that is the object created at line 6.

[Mark Smyth]

Originally posted by Sanjeev Kumar Singh:
Javier,

Only objects are eligible for the garbage collection(GC).

In the problem above(after line 8)

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

Objects created
at line 7.
at line 6.
Since the method returns the reference to the object created at line 7 so object created at line 7 will not be GCed.
The NumberFormatException created at line 6 will be GCed as the reference to the object will be destroyed after line 6.
So only one object will be GCed and that is the object created at line 6.

That depends on if a NumberFormatException is thrown or not, which we cannot say as we do not know what the String num is. If we assume it is a vaild number (which i think is the best interpretation) then 0 objects are eligible for GC arter this method. If it get thrown by parseInt then the answer is 1 as it is eligible for GC after the catch block completes.

[Javier Sanchez Cerrillo]

Thank you Sanjeev Kumar Singh & Mark Smyth. I appreciate it.