Re: Singleton Pattern

=?ISO-8859-1?Q?Arne_Vajh=F8j?= <>
Sat, 25 Nov 2006 16:45:50 -0500
andrewmcdonagh wrote:

On Nov 25, 1:55 pm, Arne Vajh?j <> wrote:

Adi wrote:

I have a question about singleton pattern. In my java user group,
someone said that this pattern should be avoided, but he didn't explain
the reason.
So I am curious here, is this statement true ?
Someone else replied that this pattern is hard to test and make other
classes tightly coupled with this Singleton class. Somehow I doubt it
but I also can find any argument for that. What I know is just because
this pattern is hard to test doesn't mean that this pattern should be
avoided right ? I use this pattern a lot of times and found it useful.
Do you have any comments ?Singleton is a valid pattern.

Most of the criticism found on the net is ridiculous ("if you implement
it wrong then it will not work" type).

The only real problem I can think of is a modifiable singleton in a
clustered environment (or other multi JVM environment).

The Singleton is a valid pattern.

The Singleton is the most used pattern.

The Singleton is the most abused pattern (e.g. used mainly for finding
something at a well know location, rather than to enforce 'just one


The majority of times, having a global access to something is the
usual reason for creating a Singleton. In these cases, its not a
singleton that was required, but a singleton containing mutliple items
- in other works a 'Container' or 'Toolbox'

As with most patterns there are a cases where it can be debated whether
a specific pattern is the best solution or not.

Singleton is probably the most widely abused. But no surprise if it
is the most widely used.

But from a practical point of view, then I would say that even
in the cases where singleton is not the best solution, then it
is usually not a bad solution either.

There are many much worse diseases than being over enthusiastic
about singletons.


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