aspose file tools*
The moose likes Programmer Certification (SCJP/OCPJP) and the fly likes Garbage Collection Big Moose Saloon
  Search | Java FAQ | Recent Topics | Flagged Topics | Hot Topics | Zero Replies
Register / Login
JavaRanch » Java Forums » Certification » Programmer Certification (SCJP/OCPJP)
Bookmark "Garbage Collection" Watch "Garbage Collection" New topic
Author

Garbage Collection

Henry Zhi Lin
Ranch Hand

Joined: Nov 04, 2008
Posts: 69
I got the following from exam lab,



How many object can be garbage collected here?

My answer is 0, but the correct answer is 1.

I am so confused here and find there is no alternative way to solve problem like this. Can anyone tip me how to solve such gc problem?

Thanks.


SCJP 5.0
Henry Wong
author
Sheriff

Joined: Sep 28, 2004
Posts: 18825
    
  40

Let's name the object OA, OB, OC, OD, etc., as they are being created. This is to distinguish them from the reference that points to it. Furthermore, we will follow the instance variable that is part of these objects, to draw all the connections.

---------------------
After...

A a1=null;
A a2=new A(new A(null));
A a3=new A(a2);

You will get...



---------------------
After ...

a1=a3;

You will get...



---------------------
After ...

a1.a=new A(null);

You will get...



----------------------
After ...
a2.a=null;

You will get ...


And as you can see, the B object is now unreachable.

Henry


Books: Java Threads, 3rd Edition, Jini in a Nutshell, and Java Gems (contributor)
Henry Zhi Lin
Ranch Hand

Joined: Nov 04, 2008
Posts: 69
Thanks Henry,

You method are really cool. It is very clear what really happens.
 
I agree. Here's the link: http://aspose.com/file-tools
 
subject: Garbage Collection