Kotlin: java.lang.UnsupportedOperationException in MutableList add element

Question

I\'m implementing a stack algorithm for study purpose in Kotlin

class Stack>(list:MutableList) {

    var items: Mutabl         


        

Answer 1

You can fix this by calling toMutableList() api rather than using smart cast (as).

Try: var initialValue = listOf< Int >(10).toMutableList()

Below is a working example:

fun main(){
    val x : List = listOf("foo", "bar", "baz")
    //val y: MutableList = x as MutableList throws UnsupportedOperationException
    val y: MutableList = x.toMutableList()
    y.add("sha")
    println(y) // [foo, bar, baz, sha]
}