Singleton

So far, I have discussed in my previous posts the Singleton Pattern, and its pros and cons. One question is still open: What alternatives for the Singleton Pattern are available? Today, I write about the Monostate Pattern and Dependency Injection.

I introduced in my last post "The Singleton", the classical Singleton and the so-called Meyers Singleton. The Singleton Pattern is highly controversial. Let me, therefore, discuss in this post the pros and cons of the Singleton.

The most controversial Design Pattern from the book  "Design Patterns: Elements of Reusable Object-Oriented Software" is the Singleton Pattern. Let me introduce it before I discuss its pros and cons.

There are a lot of issues with the singleton pattern. I'm totally aware of that. But the singleton pattern is an ideal use case for a variable, which has only to be initialized in a thread-safe way. From that point on you can use it without synchronization. So in this post, I discuss different ways to initialize a singleton in a multithreading environment. You get the performance numbers and can reason about your uses cases for the thread-safe initialization of a variable.

In case the data is not modified when shared between threads, the story is simple. The data has only to be initialized in the thread safe way. It is not necessary to use an expensive lock for each access.