Immutable and mutable lists

Collections.kt

// immutable list and mutable list
val numbersList = listOf("one", "two", "three")
val mutableNumbersList = mutableListOf("one", "two", "three")

// alter the list using add function
mutableNumbersList.add("five")

listOf(1, 5, 3).sum()  // => 9
listOf("a", "b", "cc").sumBy { it.length } // => 4

// operators
val numberList2 = numbersList + "four"
println(numberList2)
val numbersListNoTwo = numberList2 - "two"
println(numbersListNoTwo)

println(numbersListNoTwo::class) //class java.util.ArrayList
println(numbersListNoTwo.javaClass) //class java.util.ArrayList

// listOfNotNull
val notNulls = listOfNotNull(32, null, "one", null, 'd')
println("Size = ${notNulls.size}")

for (element in notNulls) {
    println(element)
}