Instruction
Heads up... You’re accessing parts of this content for free, with some sections shown as text.
Heads up... You’re accessing parts of this content for free, with some sections shown as text.
Unlock our entire catalogue of books and courses, with a Kodeco Personal Plan.
Unlock now
Kotlin offers five categories of basic types. These are:
- Numbers
- Booleans
- Characters
- Strings
- Arrays
Numbers
Kotlin offers a set of built-in types to represent numbers.
Booleans
The Boolean type in Kotlin represents objects that can hold a true or false value.
val isTrue: Boolean = true
val isFalse: Boolean = false
println(isTrue || isFalse) // prints true
println(isTrue && isFalse) // prints false
println(!isTrue) // prints false
Characters
A single character is represented by the Char type in Kotlin. Character literals always go inside single quotes: ‘Z’
Strings
A sequence of characters is called a string. In Kotlin, these are represented using the String type. String values are enclosed between double quotes: "Hello world"
val message = "Hello World!"
// Creates and prints a new String object
println(message.uppercase())
// HELLO WORLD!
// The original string remains the same
println(message)
// Hello World!
Arrays
Arrays in Kotlin are a data structure that allows you to store multiple values of the same type. They’re always mutable, and their size is defined at creation time.
var pokemonArray = arrayOf("Pikachu", "Squirtle", "Bulbasaur")
println(pokemonArray.joinToString())
// Pikachu, Squirtle, Bulbasaur
Looking at Nullability
Null safety is one of Kotlin’s marquee features. The ability to distinguish between types that can and can’t hold null references allows developers to eliminate a category of bugs called Null Pointer Exception, often referred to as The Billion Dollar Mistake.
var message: String = "Hello"
message = null // not allowed
var nullableMessage: String? = "Hello"
nullableMessage = null
println(nullableMessage) // prints null