Questions on GC from Khalid A.Mughal, Chap 9

[Anuradha Prasanna]

On page 402 & 403 of this book, there are no answers for four GC questions.

1)How many objects are eligible for GC when control reaches (1)?

public class Eligible{
public static void main(String[] args) {
for(int i=0;i<5;i++){
Eligible obj = new Eligible();
new Eligible();
}
System.gc(); // (1)
}
}

I think, 9 objects are eligible for GC. is that right?
but the answers are,
(A)0
(B)5
(c)10

can anyone tell the right answer with explanation?
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2)How many objects are eligible for GC when control reaches (1)?

public class Link {
private Link next;
Link(Link next) {this.next = next; }
public void finialize() {System.out.println("X"); }

public static void main(String[] args) {
Link p = null;
for(int i=0; i<5; i++) {
p = new Link(p);
}
System.gc();        //(1)
}
}

I think, 0 objects are eligible for GC. is that correct?

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3)How many objects are eligible for GC when control reaches (1)?

public class Elements {
public static void main(String[] args) {
int[] array = new int[4];
for(int i=0;i<4;i++) {
array[i]=i;
}
array[0]=array[1]=array[2]=array[3]=0;
System.gc();              //(1)
}
}

I think, 0 objects are eligible for GC here. Is that right?
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4) How many objects are reachable when control reaches (1)?

public class Nullify {
private static void nullify(Integer[] array) { array = null; }

public static void main(String[] args) {
Integer[] array = new Integer[4];
for(int i=0;i<4;i++){
array[i]=i;
}
nullify(array);
System.gc();        //(1)
}
}

I think 5 objects are reachable.(Integer[] obj with reference array & 4 objects pointed to by the references array[0], array[1], array[2], array[3])
is it correct?

[Burk Hufnagel]

Anuradha,

You're posting in the wrong forum. This looks like a question for the SCJP forum.

BTW, I didn't look at the rest but your answer for #1 is wrong. Take a look at the code, a new instance of Eligible gets created each time through the loop but no reference is kept. So the correct answer is the number of times the loop executes - which isn't nine.

Good luck with your studies. I recommend Kathy Sierra and Bert Bate's SCJP Study Guide - but I'm partial as I was one of the technical reviewers. Still I've used it as the textbook for an SCJP study group and everybody seemed to like the book and the folks who took the exam passed so I guess there's objective proof that it's a good book. Of course it doesn't hurt that KAthy and Bert helped write the exam...

Burk

[Bear Bibeault]

Please do not cross-post the same question in multiple forums. It wastes people's time when multiple redundant conversations take place. Please read this for more information.