JuniorTheoryCommon

What happens when you build and run this program?

KOTLIN

fun main() {
    val text: String? = null
    println("start")
    println(text!!.length)
    println("end")
}

Prints start, then a NullPointerException

Expecting start, null and end: mixing up !! with ?.. ?. gives null and goes on; !! throws NullPointerException, so end is never printed.
Expecting a compile error: !! is what lets a call on a String? compile, so the program builds, prints start and fails on the !! line.

JuniorTheoryCommon

KOTLIN

fun main() {
    val text: String? = null
    println("start")
    println(text!!.length)
    println("end")
}

Prints start, then a NullPointerException

Expecting start, null and end: mixing up !! with ?.. ?. gives null and goes on; !! throws NullPointerException, so end is never printed.
Expecting a compile error: !! is what lets a call on a String? compile, so the program builds, prints start and fails on the !! line.