Arithmetic Operators

Arithmetic in Kotlin looks exactly like what you learned in math class. Plus, minus, times, divide — it's all here, plus a few extras.

The basics

fun main() {
  val a = 10
  val b = 3

  println("a + b = ${a + b}")  // addition
  println("a - b = ${a - b}")  // subtraction
  println("a * b = ${a * b}")  // multiplication
  println("a / b = ${a / b}")  // division (integer, result is 3)
  println("a % b = ${a % b}")  // modulus (remainder, result is 1)
}
    

Notice that 10 / 3 gives you 3, not 3.333. That's because both numbers are integers, so Kotlin does integer division. Use doubles if you want decimals.

Increment and decrement

++ adds 1, -- subtracts 1. Use them before or after a variable name.

fun main() {
  var counter = 0
  counter++  // now 1
  println(counter)
  counter--  // back to 0
  println(counter)

  println(++counter)  // prints 1 (increments first, then prints)
  println(counter++)  // prints 1 (prints first, then increments)
  println(counter)    // now 2
}