static variables

[swaraj gupta]

where do the static variables are stored in java...?

[Stephan van Hulst]

I'm not exactly sure, but I believe they are stored in an instance of the Class class.

[swaraj gupta]

Hi stephan,
thanks for the reply!

You mean to say on heap. Will you more elaborate your answer ?

Stephan van Hulst wrote:I'm not exactly sure, but I believe they are stored in an instance of the Class class.

[amit mandal]

They are stored in the Class object associated with that class. Instances of Class are also stored on the heap called "permanent generation".

[Mohamed Sanaulla]

amit mandal wrote:They are stored in the Class object associated with that class.

Can someone confirm this? Or some kind of material where we can read about this. Even I never thought about this But I feel they would also be on the heap- May be all the statics in one group on the heap? That's actually coming back to what Amit said

amit mandal wrote:Instances of Class are also stored on the heap called "permanent generation".

I believe that the Object allocation and GC techniques are much complicated. There's a new generation and an old generation. Objects are allocated to the new gen. if these objects survive the GC then they are moved to the old gen.

[amit mandal]

you can read it here even though its bit confusing :

permanent generation

[Mohamed Sanaulla]

amit mandal wrote:you can read it here even though its bit confusing :

permanent generation

Thanks for sharing the article

[amit mandal]

mohamed sanaullah wrote:

amit mandal wrote:you can read it here even though its bit confusing :

permanent generation

Thanks for sharing the article

You are welcome

[swaraj gupta]

I have recently gone through an article on the same and according to that:
" Whenever a process is loaded in the RAM, we can say that the memory is roughly divided into three areas (within that process):
1> Stack
2> Heap
3> Static.
The Static which is also a part of heap is used for storing static members and is also called "High Frequency Heap."

But I have a doubt, if static members exist on heap then when does the garbage collector sweep them off the heap or it wouldn't consider them?

[amit mandal]

swaraj gupta wrote:I have recently gone through an article on the same and according to that:
" Whenever a process is loaded in the RAM, we can say that the memory is roughly divided into three areas (within that process):
1> Stack
2> Heap
3> Static.
The Static which is also a part of heap is used for storing static members and is also called "High Frequency Heap."

But I have a doubt, if static members exist on heap then when does the garbage collector sweep them off the heap or it wouldn't consider them?

I suppose the static variables reside inside the permanent generation part of the heap (which i suppose is same as the high frequency heap) and stays as long as their class objects remain there as dont forget for every class loaded the jvm creates an instance of Class. so as long as the Class object stays there, the static variable is safe from the GC.

[Mohamed Sanaulla]

swaraj gupta wrote:But I have a doubt, if static members exist on heap then when does the garbage collector sweep them off the heap or it wouldn't consider them?

I think when ever the class is unloaded by the JVM.

[swaraj gupta]

After all the discussion this is what I have concluded till now:
"There exist a separate space for static members (whether reference or variable) on the heap, which is freed when the class is unloaded by the JVM. And this reserved portion of heap for static members is never considered by Garbage Collector for garbage collection."

mohamed sanaullah wrote:

swaraj gupta wrote:But I have a doubt, if static members exist on heap then when does the garbage collector sweep them off the heap or it wouldn't consider them?

I think when ever the class is unloaded by the JVM.