LearnKotlin - Variable Assignments

var rainbowColor : String = "Blue"

rainbowColor = "Violet" 

rainbowColor
Violet

val blackColor : String = "Black"
blackColor
Black

blackColor = "Blue"
error: val cannot be reassigned
blackColor = "Blue"
^

rainbowColor = null
error: null can not be a value of a non-null type String
rainbowColor = null
               ^

var greenColor : String? = null
 
 var blueColor = null

greenColor
null

greenColor = "Green"
greenColor
Green

var listOfElements: List<String>? = null

var listOfElements1 : List<String?> = listOf(null, null)

listOfElements
listOfElements1
[null, null]

var nullTest : Int? = null
println( nullTest?.inc()?: 0)
0