Solved

Nullifying static objects

Posted on 2001-08-02
11
310 Views
Last Modified: 2011-09-20
We have designed some classes as to use singleton objects as we r using often these objects in application, but if we want to nullify it in some circumstances we couldn't do that. Even though we assigned null still it is in the memory. Is there any other way to destroy these objects or any other alternate to use instead of singleton objects?

Also whatever objects created in a static class, is still in the memory( up to close the application ) even the reference or the scope of that object gone. How to tackle this problem?
0
Comment
Question by:ksivananth
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
  • 2
  • 2
  • +2
11 Comments
 
LVL 1

Expert Comment

by:Aggarwal
ID: 6347463
The problem is the way u designed the class.

If we use static then it's life time is going to be the application. So, it can't be deleted.

please post ur code ..to get better details !!
0
 
LVL 4

Expert Comment

by:Oliver_Dornauf
ID: 6347518
Even when you nullify an Object it is decission from the jvm when to delete (garbage collection)
0
 
LVL 92

Expert Comment

by:objects
ID: 6347864
It sounds like there are still references to the object somewhere. As long as something is still referencing the static object then it will not be gc'd.

class XYZ
{
   public static XYZ getInstance();

   public void f();
}


XZY local = XYZ.getInstance();   // BAD, maintains ref

XYZ.getInstance().f();    // GOOD, no reference maintained





0
Get 15 Days FREE Full-Featured Trial

Benefit from a mission critical IT monitoring with Monitis Premium or get it FREE for your entry level monitoring needs.
-Over 200,000 users
-More than 300,000 websites monitored
-Used in 197 countries
-Recommended by 98% of users

 
LVL 92

Expert Comment

by:objects
ID: 6347871
And there's no way to force the object to be deleted.
This is up to the garbage collectors perogative.
0
 
LVL 92

Expert Comment

by:objects
ID: 6347876
If the issue is that your singleton uses lots of memory then nullify the 'internals' of the singleton object to make it available for gc even if the singleton object itself is still referenced.
0
 
LVL 4

Expert Comment

by:Oliver_Dornauf
ID: 6347882
You can give the jvm a hint to run the gc with System.gc() and than System.runFinalization().

0
 
LVL 26

Author Comment

by:ksivananth
ID: 6351284
Hi everybody,

class XYZ
{
  private XYZ xyz = null ;

  public static XYZ getInstance()
  {
    if( xyz == null )
     xyz = new XYZ() ;

    return xyz ;
  }

  public void f();

  public void close()
  {
    xyz = null ;
  }
}

  In application I am using the following statement to call the method f().

XYZ.getInstance().f();    

Sometimes I want to nullify this obj, So I am calling the close method. After calling the close method, still I am able to use the "xyz" obj without calling the getInstance() method and it didn't throw NullPointerException. So it is still in the memory.

0
 
LVL 26

Author Comment

by:ksivananth
ID: 6351287
>If the issue is that your singleton uses lots of memory >then nullify the 'internals' of the singleton
>object to make it available for gc even if the singleton >object itself is still referenced.

  What do u mean by internals? is it the obj created within XYZ, if it is that also could not nullified.
0
 
LVL 92

Accepted Solution

by:
objects earned 100 total points
ID: 6354394
> still I am able to use the "xyz" obj without calling the
> getInstance() method and it didn't throw NullPointerException.

Then you must be maintaining a reference to it. Otherwise how are accessing xyz without using getInstance().

> What do u mean by internals?

The member variables of XYZ.

0
 
LVL 1

Expert Comment

by:Moondancer
ID: 6956270
ADMINISTRATION WILL BE CONTACTING YOU SHORTLY.  Moderators Computer101 or Netminder will return to finalize these if still open in seven days.  Please post closing recommendations before that time.

Question(s) below appears to have been abandoned. Your options are:
 
1. Accept a Comment As Answer (use the button next to the Expert's name).
2. Close the question if the information was not useful to you, but may help others. You must tell the participants why you wish to do this, and allow for Expert response.  This choice will include a refund to you, and will move this question to our PAQ (Previously Asked Question) database.  If you found information outside this question thread, please add it.
3. Ask Community Support to help split points between participating experts, or just comment here with details and we'll respond with the process.
4. Delete the question (if it has no potential value for others).
   --> Post comments for expert of your intention to delete and why
   --> YOU CANNOT DELETE A QUESTION with comments; special handling by a Moderator is required.

For special handling needs, please post a zero point question in the link below and include the URL (question QID/link) that it regards with details.
http://www.experts-exchange.com/jsp/qList.jsp?ta=commspt
 
Please click this link for Help Desk, Guidelines/Member Agreement and the Question/Answer process.  http://www.experts-exchange.com/jsp/cmtyHelpDesk.jsp

Click you Member Profile to view your question history and please keep them updated. If you are a KnowledgePro user, use the Power Search option to find them.  

Questions which are LOCKED with a Proposed Answer but do not help you, should be rejected with comments added.  When you grade the question less than an A, please comment as to why.  This helps all involved, as well as others who may access this item in the future.  PLEASE DO NOT AWARD POINTS TO ME.

To view your open questions, please click the following link(s) and keep them all current with updates.
http://www.experts-exchange.com/questions/Q.20084662.html
http://www.experts-exchange.com/questions/Q.20090092.html
http://www.experts-exchange.com/questions/Q.20098515.html
http://www.experts-exchange.com/questions/Q.20153597.html
http://www.experts-exchange.com/questions/Q.20162615.html
http://www.experts-exchange.com/questions/Q.20165190.html
http://www.experts-exchange.com/questions/Q.20183658.html
http://www.experts-exchange.com/questions/Q.20290867.html




*****  E X P E R T S    P L E A S E  ******  Leave your closing recommendations if this item remains inactive another seven (7) days.  If you are interested in the cleanup effort, please click this link http://www.experts-exchange.com/jsp/qManageQuestion.jsp?ta=commspt&qid=20274643 
POINTS FOR EXPERTS awaiting comments are listed here -> http://www.experts-exchange.com/commspt/Q.20277028.html
 
Moderators will finalize this question if in @7 days Asker has not responded.  This will be moved to the PAQ (Previously Asked Questions) at zero points, deleted or awarded.
 
Thank you everyone.
 
Moondancer
Moderator @ Experts Exchange
0
 
LVL 1

Expert Comment

by:Moondancer
ID: 7118718
Zero response; finalized.
Moondancer - EE Moderator
0

Featured Post

On Demand Webinar - Networking for the Cloud Era

This webinar discusses:
-Common barriers companies experience when moving to the cloud
-How SD-WAN changes the way we look at networks
-Best practices customers should employ moving forward with cloud migration
-What happens behind the scenes of SteelConnect’s one-click button

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

By the end of 1980s, object oriented programming using languages like C++, Simula69 and ObjectPascal gained momentum. It looked like programmers finally found the perfect language. C++ successfully combined the object oriented principles of Simula w…
In this post we will learn how to connect and configure Android Device (Smartphone etc.) with Android Studio. After that we will run a simple Hello World Program.
Viewers learn about the “for” loop and how it works in Java. By comparing it to the while loop learned before, viewers can make the transition easily. You will learn about the formatting of the for loop as we write a program that prints even numbers…
Viewers will learn how to properly install Eclipse with the necessary JDK, and will take a look at an introductory Java program. Download Eclipse installation zip file: Extract files from zip file: Download and install JDK 8: Open Eclipse and …
Suggested Courses

624 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question