if-else statements

if-else statements work very much like the if-else statement you are used to from Java, with a couple of minor differences.

In Java if or else parts that are single statements can drop the curly braces. In Kotlin the curly braces are always required.

In Java if-else is always a statement. In Kotlin if-else can also be an expression that returns a value.

let admission = if (age <= 12) { 7.5 } else { 10.5 }

loops

Kotlin does not offer the traditional for loop. Instead, it uses the for-in loop.

let numbers = [1,2,3,4,5]
var sum = 0
for (number in numbers)
  sum += number
println(sum)

If you want something closer to the traditional for loop, you can iterate over a range expression.

let numbers = [1,2,3,4,5]
var sum = 0
for (n in 0..(numbers.size-1))
  sum += numbers[n]
println(sum)

Kotlin also offers a while loop that is very similar to the while loop in Java.