Singleton implementations

A singleton is a class that is instantiated exactly once (or at least, once per classloader). It is considered to be an anti-pattern by many (including me!) because it makes unit testing difficult. You can’t substitute a mock implementation for a singleton (unless it happens to implement an interface, which I haven’t seen too often). And singletons also make your APIs into liars.

However, if you do want/have to use singletons, this article discusses the best approach.

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Tags: singleton