Add LazyThreadSafeSingleton code and test

[mkdika]

Hi,

I add the lazy thread safe singleton pattern example. Please kindly check and review. Thank you.

Best regards,

Maikel

[dbacinski]

Object is also lazy at a class level, it won't get initialised until you will reference class.

See "decompiled" byte code https://stackoverflow.com/a/54053195/361832

It only makes sense if you have more then one instance field which seams very rare and potentially breaking single responsibility principle.

[mkdika]

yeah I know. It is more to variant or improvement of normal singleton pattern, and I was trying to implement the double-check locking singleton in Kotlin. Furthermore, thats why I didn't update the readme :)