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Singleton two or more instances

Harikrishna Gorrepati
Ranch Hand

Joined: Sep 23, 2010
Posts: 422
Hi, The following is asked me several times during the interview
Question : Can we have singleton with 2 instances or 3 instances or more ? How to achieve that ?
My Answer : It cannot be more than 1 instance.
But interviewers are never happy with my answer even though I gave them the Singleton code. Please let me know how to get it. Please post code which helps me a alot.


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Rob Spoor
Sheriff

Joined: Oct 27, 2005
Posts: 19649
    
  18

How does singleton allows the flexibility to create more objects if the situation changes.


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fred rosenberger
lowercase baba
Bartender

Joined: Oct 02, 2003
Posts: 11153
    
  16

Start a second JVM...


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Stephan van Hulst
Bartender

Joined: Sep 20, 2010
Posts: 3574
    
  14

Personally I've always thought of the Singleton pattern as one that generally limits the amount of instances created, but not necessarily to a single instance. The name is misleading, but the general case makes more sense for a pattern.
Matthew Brown
Bartender

Joined: Apr 06, 2010
Posts: 4339
    
    7

fred rosenberger wrote:Start a second JVM...

Or just use a second class loader?

It could be that they're thinking about distributed applications...in which case unless you're doing something clever there's nothing to stop the separate components each creating an instance.
 
It is sorta covered in the JavaRanch Style Guide.
 
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