Garbage collector!!!!!!!!!

[sunil kathuria]

following question is from mock exam -SARGA.com
At what point is the object anObj available for garbage collection.
01: public class Base{
02:
03: private void test() {
04:
05: if(true) {
06: String anObj = "sample";
07: String locObj = anObj;
08: anObj.trim();
09: anObj = null;
10: locObj.trim();
11: }
12: }
13:
14: static public void main(String[] a) {
15: new Base().test();
16: }
17:
18: }
Select most appropriate answer
a) After line 7
b) After line 8
c) After line 9
d) After line 10
e) After line 11

answer given is -- >e
but whereever i think it should be c as when we set "anObj" to null it will be available for gc.
pl. tell me the right answer and correct me if wrong
thanks in adv.
sunil

[Andy Skalkin]

It is not available for GC after we set anObj to null because we still have this object's reference stored in locObj.
P.S. btw I'm not sure if strings from the string pool are available for GC ...

[Albert Gray]

Look at your code (I just added 2 lines for printing the object). Now I still see anObj still printing "sample", after line 11, meaning that it will not be Gced after line 11. So my answer is none of them.
public class Base{
private void test() {
if(true) {
String anObj = "sample";
String locObj = anObj;
anObj.trim();
anObj = null;
locObj.trim();
System.out.println(anObj);//null
System.out.println(locObj);//sample
}
}
static public void main(String[] a) {
new Base().test();
}
}
Albert

Originally posted by sunil kathuria:
following question is from mock exam -SARGA.com
At what point is the object anObj available for garbage collection.
01: public class Base{
02:
03: private void test() {
04:
05: if(true) {
06: String anObj = "sample";
07: String locObj = anObj;
08: anObj.trim();
09: anObj = null;
10: locObj.trim();
11: }
12: }
13:
14: static public void main(String[] a) {
15: new Base().test();
16: }
17:
18: }
Select most appropriate answer
a) After line 7
b) After line 8
c) After line 9
d) After line 10
e) After line 11

answer given is -- >e
but whereever i think it should be c as when we set "anObj" to null it will be available for gc.
pl. tell me the right answer and correct me if wrong
thanks in adv.
sunil

[Anshul Manisha]

Hi Albert,
I think you are wrong. When a trim does not remove any spaces from the string then it returns the reference to the string itself. So at line 10 locObj is still referring to "sample". Since after line 11 (closing }) it goes out of scope it would be eligible for garbage collection.
please correct me if I am wrong.
regards

Originally posted by Albert Gray:
Look at your code (I just added 2 lines for printing the object). Now I still see anObj still printing "sample", after line 11, meaning that it will not be Gced after line 11. So my answer is none of them.
public class Base{
private void test() {
if(true) {
String anObj = "sample";
String locObj = anObj;
anObj.trim();
anObj = null;
locObj.trim();
System.out.println(anObj);//null
System.out.println(locObj);//sample
}
}
static public void main(String[] a) {
new Base().test();
}
}
Albert

[Jane Griscti]

Hi Anshul,
Have to agree with you. 'anObj' is declared in the 'if' block and as no reference to it was passed to any variable outside the block it would be eligible for gc when the 'if' completes.
------------------
Jane Griscti
Sun Certified Programmer for the Java� 2 Platform