Mastering Kotlin

Null-safe calls

With a non-null type, you may safely call methods or access properties on a variable without worrying about NullPointerException. In this snippet, languages is inferred to be List<String>. Because languages is of a non-null type, the isNotEmpty() method may be called without worrying about NullPointerException, as follows:

fun main(args: Array<String>) {    var languages = listOf("Kotlin", "Java", "c++")    languages.isNotEmpty() // okay}

If the list were defined as List<String>?, this would not be the case. In this case, calling companies.isNotEmpty() would result in a compiler error. Because the compiler knows the value might be null, it will require you to handle that possibility in some way:

fun main(args: Array<String>) {