A function type that doesn't return anything must use the return type Unit. You put the type(s) of the parameter(s) in the left-side parenthesis and the return type on the right side. as a parameter to another function) or as the type of a variable holding a function reference. Ī function type is a special notation Kotlin uses to represent a function - basically its signature - that can be used to declare a function (e.g. 🔖 I created this Table of Contents using BitDownToc. To better understand what it means, and why it is so cool, let's go through the theory: what are function types, why they matter, and how they relate to lambdas and higher order functions.ĭid I lose you? Then read on! Everything will become clear, I promise! 😊

This is one of the idioms of functional programming, a programming style that I love.

Normally,types of String are not nullable.Kotlin treats functions as first-class citizens.įirst-class means functions can be stored in variables and data structures and can be passed as arguments to and returned from other functions ( higher-order functions). Kotlin types system differentiates between references which can hold null (nullable reference) and which cannot hold null (non null reference). Kotlin Nullable Types and Non-Nullable Types

Use of external java code as Kotlin is Java interoperability.

An uninitialized of this operator which is available in a constructor passed and used somewhere.

An forcefully call to throw NullPointerException().

NullPointerException can only possible on following causes: Kotlin's type system is aimed to eliminate NullPointerException form the code. Kotlin compiler throws NullPointerException immediately if it found any null argument is passed without executing any other statements. Kotlin null safety is a procedure to eliminate the risk of null reference from the code.

Null in kotlin