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Garbage Collection

 
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Hi All,
I came across this question in Exam Prep by Bill Brogden. Practice test 1 question no.27.
____________________________________________________________
Here is a method which creates a number of String objects in the course of printing a series of messages.
1: public void soundOff() {
2: for (int i=1;i<10;i++) {
3: String tmp = Integer.toString(i);
4: System.out.print(tmp + ", ");
5: }
6: System.out.println("10");
7: }
When the program reaches line 6, how many of the String objects created in line 3 are eligible for garbage collection? Assume that the System.out object is not keeping a reference.
a. none
b. 1
c. 8
d. 9
____________________________________________________________
The given answer is c.8,
but I think d.9 is correct. Could some one tell me the correct answer?
Thanks,
Malar.
 
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variables that are local to methods are normally gced when the method returns. However, an optimizing compiler could gc them when leaving a specific block (in this case the for loop). BUT in the case of a normal compiler, at line 6 tmp (although not in the scope anymore) is still having a reference to the last created String instance, namely "9,". So at line six, again in the case of an non-optimizing compiler, there are only 8 String objects available for garbage collection ("1," to "8,")
HIH
------------------
Valentin Crettaz
Sun Certified Programmer for Java 2 Platform
[This message has been edited by Valentin Crettaz (edited November 05, 2001).]
 
Malar Ravi
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Hi Valentin,
So if nothing is mentioned about the compiler does that mean we have to consider non-optimizing compiler for questions related to GC?
Thanks,
Malar.
 
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Hi Malar
Because we can't asumme anything about the compiler I think the correct answer is 9 because variables are made eligable for gc after the program has passed its scope. I hope in the exam the answer will be 9.
 
"The Hood"
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The variable is out of scope for you, but it lives on a stack that is associated with a "Frame" (not a GUI type frame ). The Frame is associated with a Method and holds the reference to the local variable until the method goes out of scope.
So the answer is 8.
 
Valentin Crettaz
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Good explanation Cindy !

------------------
Valentin Crettaz
Sun Certified Programmer for Java 2 Platform
 
Jose Botella
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Thanks Cindy
 
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