interface Movable {
    var maxSpeed: Int
    var wheels: Int
    fun move(movable: Movable): String
}

class Car(_name: String, override var wheels: Int = 4) : Movable {
    override var maxSpeed: Int
        get() = 1
        set(value) {}

    override fun move(movable: Movable): String {
    }

}

Kotlin規定。所有的接口屬性和函數都要使用override關鍵字。接口中定義的函數并不需要open關鍵字修飾。他們默認就是open的

默認實現

interface Movable {
    val maxSpeed: Int
        get() = (1..500).random()
    var wheels: Int
    fun move(movable: Movable): String
}

class Car(_name: String, override var wheels: Int = 4) : Movable {
    override var maxSpeed: Int
        get() = super.maxSpeed
        set(value) {}

    override fun move(movable: Movable): String {
        return "";
    }

}

fun main() {
    (1..100).forEach {
        println((1..3).random())
    }
}

?和Java不同。kotlin的接口可以實現默認參數。