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What is there behind List?

I’m following an Android course on Udacity and I encountered this code:

var listResult: List<MarsProperty> = MarsApi.retrofitService.getProperties()

value = "Success: ${listResult.size} Mars properties retrieved"

We are getting a List object but I don’t understand where is the logic of the methods in the interface. I know that


is an interface (

interface List<out E> : Collection<E>

) and it defines some methods like



public fun isEmpty(): Boolean

that don’t have a logic. I can understand this work if I would call a class like


in Java that implements the interface and implements its methods, but how does it work here?

submitted by /u/____Mattia____
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