class
- Kotlin course
- Beginner
- Lesson 106/116
- 5 min
Learn to define classes with class.
class: define a new type
A class defines a new type; inside it, data and behaviour live together. In its simplest form a class can have an empty body.
class Person
val p = Person()This declaration creates a new type called Person. The call Person() creates an instance of this type. Class names usually start with an uppercase letter; this is a common convention.
Creating instances
To create an instance of a class you call the class name with parentheses. An instance is a concrete object of that class.
val p = Person()
val q = Person()
// p and q are different instancesEach call creates a new object; two instances are independent. You assign the instance to a val variable to reuse it. In later lessons you will add properties and behaviour to the instance.
Practice Define a class and create an instance
Define an empty-bodied class called Person. In main create an instance and print "Person ready" with println.
Starter code
fun main() {
// Define a Person class and create an instance, print ready
}Sample solution
class Person
fun main() {
val p = Person()
println("Person ready")
}Expected output
Kişi hazır
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What does class Person define?
- A function
- A template type Correct answer
- A constant
- An interface
Explanation: class defines a new type as a template.
2 Fill in the blank: declare a class
class ____ { }class Person { }Explanation: class Person declares a new type.
3 Match concept to meaning
| Term | Meaning |
|---|---|
class |
Template |
Person() |
Instance |
Person |
Type name |
val p |
Variable |