val numList1 = mutableListOf(
    1,2,3
)

val numList2 = mutableListOf(
   1,2,3,4
)


fun main(args: Array<String>) {

   val result = numList1.union(numList2)

    result.forEach {
        println(it)
    }

    println("<---------------->")

    val result2 = numList1.intersect(numList2)

    result2.forEach {
        println(it)
    }

}

1
2
3
4
<---------------->
1
2
3