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Kotlin Interfaces
Kotlin Interfaces – Custom Behavior Contracts
An interface in Kotlin defines a set of rules or actions that a class must follow, without giving the actual working details.
Think of it like a blueprint: it lists what should be done, but not how.
Declaring an Interface
interface Vehicle {
fun drive()
fun stop()
}
Vehicle interface just says any class using it must have drive() and stop() methods.
Implementing an Interface
class Car : Vehicle {
override fun drive() {
println("Car is moving")
}
override fun stop() {
println("Car has stopped")
}
}
The Car class fulfills the contract by writing its own version of the methods.
Multiple Interfaces? No Problem!
Kotlin supports multiple interfaces:
interface Electric {
fun charge()
}
class Tesla : Vehicle, Electric {
override fun drive() = println("Tesla zooms silently")
override fun stop() = println("Tesla halts with regen brakes")
override fun charge() = println("Charging Tesla battery")
}
A class can combine behaviors from different interfaces.
| Feature | Interface | Class |
|---|---|---|
| Can hold state? | No (mostly) | Yes |
| Method body? | Optional | Yes (always) |
| Multiple allowed? | Yes (many) | No (only one) |
Why Use Interfaces?
- Promote reusability
- Improve flexibility
- Encourage clean structure
- Useful for polymorphism
Prefer Learning by Watching?
Watch these YouTube tutorials to understand KOTLIN Tutorial visually:
What You'll Learn:
- 📌 #32 Kotlin Tutorial | Interface
- 📌 How to Implement an Interface in Kotlin