How to implement singleton without using static/global variable? Possible?

Question

How to implement singleton without using static/global variable? Possible?

This is an interview question...

Answer 1

Dependency injection is one possibility. Since your question is not specific to any programming language, I am not posting framework specific syntax (such as Ninject)

Answer 2

Store the singleton in a file.

Answer 3

No. You need a place to store the singleton.