Kotlin by Example: Interfaces
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A simple interface looks like this. |
interface VehicleInterface {
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An interface can define methods and properties that implementations need to define. |
val acceleration: Int
fun alarm(): String
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It is possible to provide default implementations for properties and methods. |
val looksLike: String get() = "car"
fun engine(): String {
return "VROOM"
}
}
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A class can define zero or multiple interfaces. If a class implements multiple interfaces which both have a default implementation for some method or property, the implementation must provide an implementation. The default implementation of |
class PetrolCar : VehicleInterface {
override val acceleration = 50
override fun alarm(): String {
return "WIIIUUUIIIUUU"
}
}
class ElectricCar : VehicleInterface {
override val acceleration = 1000
override fun alarm(): String {
return "WIIIUUUIIIUUU"
}
override fun engine(): String {
return "zzzzzz"
}
}
fun main() {
val car = PetrolCar()
println("A car looks like a ${car.looksLike},")
println("its engine sounds like ${car.engine()},")
println("its alarm sounds like ${car.alarm()},")
println("and accelerates at ${car.acceleration}.")
println()
val ev = ElectricCar()
println("An EV looks like a ${ev.looksLike},")
println("its engine sounds like ${ev.engine()},")
println("its alarm sounds like ${ev.alarm()},")
println("and accelerates at ${ev.acceleration}.")
}
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$ kotlinc main.kt -include-runtime -d main.jar
$ java -jar Main.jar
A car looks like a car,
its engine sounds like VROOM,
its alarm sounds like WIIIUUUIIIUUU,
and accelerates at 50.
An EV looks like a car,
its engine sounds like zzzzzz,
its alarm sounds like WIIIUUUIIIUUU,
and accelerates at 1000.
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