Objects Eligible for GC

[Peter Swiss]

Here is the question from K&B book page 275

class Beta {}
class Alpha {
   static Beta b1;
   Beta b2;
 }

public class Tester{

public static void main(String [] args){
   Beta b1 = new Beta();   Beta b2 = new Beta();
   Alpha a1 = new Alpha();    Alpha a2 = new Alpha();
   a1.b1 = b1;
   a1.b2 = b1;
   a2.b2 = b2;
   a1=null;  b1=null;  b2=null;
   //do stuff
}

How many objects are eligible for GC?

In my opinion,
Object refered by a2 is accessible
Object refered by b2 is accessible via a2.b2
Object refered by a1 is not accessible

What about Object refered by b1???

Please reply. Thank you.

[Riza Aktunc]

Object referred by b1 is accessable through a2.b1 since b1 is a static variable.

a1.b1 = b1; this statement makes the static b1 referance to refer the object referred by b1 in the main method. So it automaticly says that a2.b1 = b1; too.

[Peter Swiss]

Oh yes, static variable is associated with the class! Cool.

Thanks!

[John Schubert]

So the answer is one, just the object referred by a1 is GCable.

[Ram Reddy]

I think the answer is 2.
Objects referenced by a1 & b2.

[John Schubert]

I think the answer is 2.
Objects referenced by a1 & b2.

No, only a1 is GCable. The object referenced by b2 is also referenced by the Alpha a2.

[Ram Reddy]

My bad.
you are correct John...