garbage collection

[Mary Robert]

Hi all..
I was just reading abt garbage collection in Marcus's notes. i've a small doubt regarding objects .. like when will they be eligible for garbage collection. Suppose , we have a method like..
public boolean aMethod()
{
Object ob = new Object();
// some code
ob = null;
return false;
}
now, when the object ob will be eligible for garbage collection?
Is it after the statement ob = null or when the method returns?
Please clarify...
Thank U
Mary.

[Junaid Bhatra]

AS soon as you set obj=null, the object being referenced by obj is eligible for garbage collection. However the JLS does NOT specify how garbage collection is to be implemented. Hence some JVM's may choose to garbage-collect the object after the method returns, while some may immediately garbage-collect it. From the stand-point of the SCJP, the object is eligible for gc as soon as you set it's reference to null.

[Charlie Swanson]

Hello, I just had a question about this question. I understand that an object will be garbage collected when it equal null. At the end of a method, assuming the local object is reference on the last line of the method. Will the object in the method, be eligible for garbage collection when the method exits, since it is a local object.

[Sujit Kurtadikar]

The object will be eligible for GC as soon as the reference count for that object becomes 0 (zero)
In the give code, object will be eligible after line ob = null; it executed, but there is no way to know that when the object is extracted collected, it may be collected any time after it becomes eligible for GC.
Object o1 = new Emp(); //1
Object o2 = o1; //2
o1 = null; //3
In this case, object refered by o1 will not be eligible after line 3, b'cos variable o2 is still refering that object.
Object declared in method :
Object declared in method as local variable will be eligible for GC, after that method completes execution. sucj local object have validity in scope of method.
class Q1
{
void aMethod()
{
Emp e1 = new Emp(); //1
//few lines of code here
//2
}
}
In this example, object refered by object variable e1, is eligible for GC after line 2, i.e. when aMethod() completes execution.