Size of a empty class

Hi, Can anybody tell me what would be the size of a instance of a class in java that contains no instance variables and methods?.( That is I call it as empty class though it extends java.lang.Object).

What do you mean by size? The size of the file on disk?

Size mean the amount of memory (in bytes) allocated on heap by JVM.

Using instrumentation (with getObjectSize) it seems an instance of EmtpyClass uses as much heap space as an instance of Object...
-> http://www.javaspecialists.co.za/archive/Issue142.html

I am not sure, but this may vary depending on the specific JVM you are using. I don't think there is a single answer of "It will always be X bytes".

Ok. Let me get answer for generalized question.
How to find how much memory an object aquires?

I agree with Fred.

You can try to see if Java Visual VM (1.6) can do that.

I am unaware of any methods which can allow you to do through the program itself.

Avishkar Nikale wrote:I am unaware of any methods which can allow you to do through the program itself.

Did I already mention instrumentation and using method 'getObjectSize'?

I dont think getting the size of an object would be possible. All you can do is get the total,max & free memory of the JVM.
You can find those methods in java.lang.Runtime class.

Peter Taucher wrote:
Did I already mention instrumentation and using method 'getObjectSize'?

Peter,

I am aware about it now. I had never used the java.lang.instrument package.

Thanks a lot !!!