hi guys！when you want to create a Singleton ，which...

# android

[dididi]

hi guys！when you want to create a Singleton ，which one would you choose？ ‘object’ or ‘companion object’？ what is different？

[Allan Wang]

If the object is closely related with another class, you can make it a companion. If it's independent, you can make it its own object

[Allan Wang]

It's similar to how you would choose to make a public static utility class or a static class inside another class. It's more or less just naming

[dididi]

thank you for your answer！i wrote a double-checked Singleton with ‘object’ and ‘companion object’ , and decompiler them to java, object use static block to init , companion object use inner class and static variable to init , one more question: whats difference between static block and static variable?

[Allan Wang]

This is more of a java question and you’d have to look up the order for which static blocks are called. See

https://stackoverflow.com/questions/40700373/the-execute-order-of-the-static-methodjava

[dididi]

kotlin doc explain it object and companion object: object declarations are initialized lazily, when accessed for the first time;
a companion object is initialized when the corresponding class is loaded (resolved), matching the semantics of a Java static initializer.
http://kotlinlang.org/docs/reference/object-declarations.html

[dididi]

But i think both of them init when the class is loaded ?

[dididi]

sorry! I misunderstood the explain! i got it!