while and do..while

Kotlin’s while and do..while constructs are just like Java.

while

Here’s while:

var i = 1

while (i < 5) {
    println(i++)
}

Here’s its output in the REPL:

>>> while (i < 5) {
...     println(i++)
... }
1
2
3
4

do..while

Here’s do..while:

var i = 1

do {
    println(i++)
} while (i < 0)

and its REPL output:

>>> do {
...     println(i++)
... } while (i < 0)
1

Notice that do..while always runs at least once because it executes its body before running the first test.