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some doubts in core java

Kaushik Baral
Greenhorn

Joined: Aug 08, 2009
Posts: 23
hi,
i have some doubts in some core java topics. i am writing list of the questions. thanks a lot in advance.

1) can we clone a singleton instance? do we need to implement clonable interface for this? if so then why because clone method is available in Object class.
2) If we clone the object it will loose its singleton property. so to stop cloning what we can do?
3) if we serialize an object and De serialize it twice how many objects we will get?

fred rosenberger
lowercase baba
Bartender

Joined: Oct 02, 2003
Posts: 11406
    
  16

If an object is meant to be a singleton, then you probably don't want to let it be cloned. Therefore, you should not implement the cloneable interface. And if you don't, calling the clone() method inherited from the Object class throws an exception, if i recall correctly.

So the answer to #2 is to not implement the cloneable interface.


There are only two hard things in computer science: cache invalidation, naming things, and off-by-one errors
Minh Nam
Ranch Hand

Joined: Sep 10, 2011
Posts: 57
Kaushik Baral wrote:
3) if we serialize an object and De serialize it twice how many objects we will get?


Why don't you write some code to find the answer?


Advanced java topics
Ove Lindström
Ranch Hand

Joined: Mar 10, 2008
Posts: 326

Good article on clone in Java.

http://en.wikipedia.org/wiki/Clone_%28Java_method%29
Campbell Ritchie
Sheriff

Joined: Oct 13, 2005
Posts: 39395
    
  28
Or you might find the 3rd chapter of the old edition of Bloch's Effective Java™ here. That tells you about clone(). Remember it is the old edition.
 
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