Kotlin Video series – null safety

This is the eleventh part of the video series on Kotlin language.
Read and watch the other parts here.

We discuss null safety in Kotlin language. Kotlin treats nullable and non-nullable references differently. ie., You cannot assign null to references. Compiler doesn’t like it. If you have a reference that can accept null value too, then the question-mark(?) comes into picture. Null comparisons have also been made simple thanks to Elvis operator (?:)

The examples used in the video are given below

fun main(args:Array<String>){
   var name:String = "Ram"
   //name = null
   //This condition is always true
   if(name != null){
	println(name)
   }
	
   var anotherName:String? = "John"
   if(anotherName != null){
	println(anotherName)
    }
    anotherName = null
    println(anotherName)
	
    println(anotherName?.length ?: -1)
}

Nullable types can be passed to functions and also returned as output

  fun calculateLength(value:String?):Int?{
     return value?.length
  }
  fun main(args:Array<String>){
     println(calculateLength("Joe"))
     println(calculateLength(null))
  }

You can find the video here.