How can a singleton class use an interface?

java interface singleton class-design
AJ. picture AJ. · Sep 30, 2009 · Viewed 28.1k times · Source

I read at many places that singletons can use interfaces. Some how I am unable to comprehend this.

Answer

nkr1pt picture nkr1pt · Sep 30, 2009

Every class can implement an interface, and a Singleton is just a "normal" class that makes sure that only one instance of it exists at any point in time apart from the other business logic it may implement. This also means that a Singleton has at least 2 responsibities and this is not good OO design as classes should only have 1 responsibility and make sure they are good at that responsibility, but that is another discussion.

Related questions

Implements vs extends: When to use? What's the difference?

Please explain in an easy to understand language or a link to some article.

Read More
How should I have explained the difference between an Interface and an Abstract class?

In one of my interviews, I have been asked to explain the difference between an Interface and an Abstract class. Here's my response: Methods of a Java interface are implicitly abstract and cannot have implementations. A Java abstract class can …

Read More
Type List vs type ArrayList in Java

(1) List<?> myList = new ArrayList<?>(); (2) ArrayList<?> myList = new ArrayList<?>(); I understand that with (1), implementations of the List interface can be swapped. It seems that (1) is typically used in an application regardless of need (…

Read More