These basic types include numbers, characters, and booleans. In Kotlin, several basic types are available to use when declaring variables and constants. Simply put, a type is a category of data that a variable or expression can hold. The data type is one of the most fundamental concepts in any programming language. With the introduction out of the way, let's get started! Basic Types Hence, the compiler can track values which can be null and warn you if you're trying to access nullable value, preventing an NullPointerException from happening. It makes a clear distinction between references that can hold null values (nullable references) and those that cannot (non-null references).

The type system of Kotlin is designed to provide an effective way to manage null references. But don't worry, Kotlin offers a solution for this. According to a survey, NullPointerException is the most common exception in java applications. Accessing a type that can be null can result in a null reference exception, commonly known as a NullPointerException. Coming to the second part of our article, we'll discuss why we need to be concerned with null safety. In programming, a type system is a set of rules that determine how data is stored, modified, and used. In this article, we're going to dive deep into Kotlin's type system and learn all about null safety.įirst, let's define what a type system is. In the previous articles, we covered some basics of Kotlin and OOPS. var a: String? = 'abc' // can be set null a = null // value set to null val l = if (a != null) a.Welcome to the fourth article in this series on Android Development. To avoid this error we have to check if b is null and handle two cases in a respective manner.

To allow nulls, we have to declare a variable as a nullable string, which can be done by adding a “?” to the data type i.e, “String? ”.The nullable counterpart of some type A is denoted as A? var a: String? = 'abc' // this is a nullable string b = null // value is set to null print(a) // null printedīut in this case, there are chances of NPE error when a method or property is accessed. In Kotlin a normal data type like string cannot store a null value and trying to do so will cause an error. This is done to eliminate the NullPointerException error in the code which is common in other programming languages like Java. In Kotlin by default, the data types are of non-nullable types i.e trying to assign a value as null would cause an error.

Kotlin nullable types