![]() To define a nullable variable, we must append a question mark(?) to the type declaration: fun main() ") // Throws NullPointerExceptionĮxception in thread "main" kotlin. Here, by default compiler considers name variable as a Non-Null reference. Output: Error:(6, 27) Kotlin: Null can not be a value of a non-null type String Var name:String = null // COMPILATION ERROR For example, Nullable string can be declared by. We cannot assign a null value to a variable because it’ll throw a compilation error( NPE): To make a reference as null, kotlin has separate reference type for each of the type known as Nullable type. In Kotlin, all variables are non-nullable by default. ![]() Non-Null Reference: These references can’t hold null values.Nullable Reference: These references can hold null values.In Kotlin, the type system differentiates between two types of references: Kotlin’s comes with null safety to eliminate NullPointerException’s from our code. In Kotlin when you declare a variable, a field or a function parameter, by default they cannot be null. ("Student name (Uppercase): " + name.toUpperCase()) Įxception in thread "main" Let’s understand with simple example in Java where NullPointerException occurs: In Java this would be the equivalent of a NullPointerException or NPE. One of the most common pitfalls in many programming languages, including Java, is that accessing a member of a null reference will result in a null reference exception. ![]() Null Safety in Kotlin is to eliminate the risk of occurrence of NullPointerException from code. ![]()
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