JuniorTheoryCommon

What does the program print (lines separated by spaces)?

KOTLIN

fun main() {
    val s = "hello"
    s.uppercase()
    println(s)
    println(s.uppercase())
}

hello HELLO

Expecting HELLO HELLO: thinking uppercase() changes s. It returns a new string, and without val upper = … or a println that result is lost.
Expecting a compile error because s is a val: val only forbids s = …; calling a function that returns a new string is allowed.

JuniorTheoryCommon

KOTLIN

fun main() {
    val s = "hello"
    s.uppercase()
    println(s)
    println(s.uppercase())
}

hello HELLO

Expecting HELLO HELLO: thinking uppercase() changes s. It returns a new string, and without val upper = … or a println that result is lost.
Expecting a compile error because s is a val: val only forbids s = …; calling a function that returns a new string is allowed.