Operators in Kotlin

Operators are used to perform operations on operands(value and variable). There are following operators in Kotlin-

• Arithmetic Operators
• Assignment Operators
• Logical operators
• Comparison and Equality Operators
• Unary prefix and Increment/Decrement
• 'In' operator
• Indexed access operator
• Invoke operator

1. Arithmetic Operators

If you want to perform basic algebraic operations like +, -, * and / in Kotlin then use arithmetic operators.

Operator Usage Description Translates to
+ value1 + value2 Adds value1 and value2. value1.plus(value2)
- value1 - value2 Subtract value2 from value1. value1.minus(value2)
* value1 * value2 Multiplies value1 by value2. value1.times(value2)
/ value1 / value2 Divides value1 by value2. value1.div(value2)
% value1 % value2 Calculates the remainder of dividing value1 by value2. value1.mod(value2)

Example of Arithmetic Operators

fun main(args: Array) {

val num1 = 200
val num2 = 10
var result: Double

result = num1 + num2

result = num1 - num2
println("Subtraction = \$result")

result = num1 * num2
println("Multiplication = \$result")

result = num1 / num2
println("Division = \$result")

result = num1 % num2
println("Remainder = \$result")
}

Output

Subtraction = 190
Multiplication = 2000
Division = 20
Remainder = 0

2. Assignment Operators

The assignment operator is used to assign the value to a variable or operand. Let's see how we can use it-

val i = 10

Here, 10 is assigned to variable i using = operator.

Operator Usage Description Translates to
+= value1 += value2 value1 = value1 + value2 value1.plusAssign(value2)
-= value1 -= value2 value1 = value1 - value2 value1.minusAssign(value2)
*= value1 *= value2 value1 = value1 * value2 value1.timesAssign(value2)
/= value1 /= value2 value1 = value1 / value2 value1.divAssign(value2)
%= value1 %= value2 value1 = value1 % value2 value1.modAssign(value2)

Example in Assignment Operators

fun main(args: Array) {
var num = 15

number += 5    // num = num+5
println("num  = \$num")
}

Output

20

3. Logical Operators

Logical operators are used in control flow such as if expression, when expression, and loop. There two types of logical operators in Kotlin- ||(Logical OR) and &&(Logical AND).

Operator Usage Description
Logical OR(||) expression1 || expression2 It checks the second operand when the first operand is false. If the first operand evaluates to true, then the second operand is not even checked.
Logical AND(&&) expression1 && expression2 It checks the second operand when the first operand turns out to be true. If the first operand evaluates to false, then the second operand is not even checked.

Example of Logical Operator

fun main(args: Array){
val p = 5
val q = 8
val r = -2
val result: Boolean

// result is true is a is largest
result = (p>q) && (p>r) // result = (p>q) and (p>r)
println(result)
}

Output

true

6. 'In' Operator

The operator in is used to check whether an object belongs to a collection.

Operator Expression Translates to
in value1 in value2 value2.contains(value1)
!in value1 !in value2 !value2.contains(value1)

Example of In Operator

fun main(args: Array){
val numbers = intArrayOf(2, 4, 40, -3)

if (4 in numbers){
println("numbers array contains 4.")
}
}

Output

numbers array contains 4.

7. Index access Operator

Expression Translates to
a[i] a.get(i)
a[i, n] a.get(i, n)
a[i1, i2, ..., in] a.get(i1, i2, ..., in)
a[i] = b a.set(i, b)
a[i, n] = b a.set(i, n, b)
a[i1, i2, ..., in] = b a.set(i1, i2, ..., in, b)

Example of In Operator

fun main(args: Array){

val p  = intArrayOf(1, 2, 3, 4, - 1)
println(p)
p= 12
println(p)
}

Output

2
12

8. Invoke Operator

Expression Translates to
a() a.invoke()
a(i) a.invoke(i)
a(i1, i2, ..., in) a.inkove(i1, i2, ..., in)
a[i] = b a.set(i, b)

Parentheses are translated to calls to invoke number of arguments.