When would a Singleton not work as a Singleton?

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cracking singleton with other ways

Can anyone please tell me when a Singleton would not work as a Singleton?

That would be when it is not written correctly. Do you have a specific example you would like an explanation about? — Mat, Jul 26 '12 at 07:03
A singleton would not work as a singleton the moment you create two instances of it. — aioobe, Jul 26 '12 at 07:03
A singleton won't be a singleton if it does not work as a Singleton. :) — Akhi, Jul 26 '12 at 07:04
Singletons in Java can be implemented in different ways. Add details about exactly what implementation you are referring to. — Rajesh J Advani, Jul 26 '12 at 07:07
This one was asked a few hours ago: [Cracking Singleton with Other Ways](http://stackoverflow.com/q/11654876/697630). — Edwin Dalorzo, Jul 26 '12 at 07:16
Reminds of the old joke... Q: When is a door not a door? A: When its ajar. ;) — Peter Lawrey, Jul 26 '12 at 07:58

score 10 · Answer 1 · edited Aug 26 '16 at 17:36

10

There is very good post published on Sun website by author Joshua Fox. Please go through this.

below are some of them scenario when your Singleton doesn't behave like.

Multiple Singletons in Two or More Virtual Machines
Multiple Singletons Simultaneously Loaded by Different Class Loaders
Singleton Classes Destroyed by Garbage Collection, then Reloaded
Purposely Reloaded Singleton Classes
Copies of a Singleton Object that has Undergone Serialization and Deserialization

edited Aug 26 '16 at 17:36

dma_k

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answered Jul 26 '12 at 07:06

amicngh

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The link given by @amicngh appears to have changed since Oracle took ownership of Java. I believe the new link is http://www.oracle.com/technetwork/articles/java/singleton-1577166.html – HairOfTheDog Apr 21 '16 at 18:56

score 3 · Answer 2 · answered Jul 26 '12 at 07:05

A singleton (in Java land) wouldn't work as a singleton if a given class is loaded by multiple class-loaders. Since a single class can exist (or can be loaded) in multiple classloaders, it's quite possible to have "multiple" instances of a "supposedly" singleton class for a given JVM instance. But this is a pretty rare case and doesn't happen a lot. :)

score 0 · Answer 3 · answered Jul 26 '12 at 07:08

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If you are able to create more than one instance of the class then it doesn't remain singleton by using ways like cloning, De-serialization etc.

answered Jul 26 '12 at 07:08

Bharat Sinha

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When would a Singleton not work as a Singleton?

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