What does ?: do in Kotlin? (Elvis Operator)

Question

I can\'t figure out what ?: does in for example this case

val list = mutableList ?: mutableListOf() 

and why can it be modifi

Answer 1

Basically, if the left side of Elvis returns null for some reason, returns the right side instead.

i.e.

val number: Int? = null
println(number ?: "Number is null")

So, if number is NOT null, it will print number, otherwise will print "Number is null".