Java Singleton Design Pattern : Questions

Question

I had an interview recently and he asked me about Singleton Design Patterns about how are they implemented and I told him that using static variables and static methods we can i

Answer 1

Singleton is commonly implemented by having a static instance object (private SingletonType SingletonType.instance) that is lazily instantiated via a static SingletonType SingletonType.getInstance() method. There are many pitfalls to using singletons, so many, in fact, that many consider singleton to be a design anti-pattern. Given the questions about Spring, the interviewer probably was looking for an understanding not only of singletons but also their pitfalls as well as a workaround for these pitfalls known as dependency injection. You may find the video on the Google Guice page particularly helpful in understanding the pitfalls of singletons and how DI addresses this.