Kotlin – if-else Expression

In Kotlin, if is an expression is which returns a value. It is used for control the flow of program structure. There is various type of if expression in Kotlin.

  1. if-else expression
  2. if-else if-else ladder expression
  3. nested if expression

Traditional if Statement

Syntax of traditional if statement

if(condation){
//code statement
}

Syntax of traditional if else statement

if(condation){
//code statement
}
else{
//code statement
}

Kotlin if-else Expression

As if is an expression it is not used as standalone, it is used with if-else expression and the result of an if-else expression is assign into a variable.Syntax of if-else expression

val returnValue = if (condation) {
     //code statement
    } else {
     // code statement
    }
    println(returnValue)

Kotlin if-else Expression Example

Let’s see an example of if-else expression.

fun main(args: Array<String>) {
        val num1 = 10
        val num2 =20
        val result = if (num1 > num2) {
            "$num1 is greater than $num2"
        } else {
            "$num1 is smaller than $num2"
        }
        println(result)
}

Output :

10 is smaller than 20

We can remove the curly braces of if-else body by writing if expression in only one statement.

fun main(args: Array<String>) {
        val num1 = 10
        val num2 =20
        val result = if (num1 > num2) "$num1 is greater than $num2" else "$num1 is smaller than $num2"
        println(result)
}

Using if-else expression in one single line statement is like ternary operator in Java. Kotlin does not support any ternary operator.Kotlin if-else if-else Ladder ExpressionLet’s see an example of if-else if-else ladder expression.

fun main(args: Array<String>) {
    val num = 10
    val result = if (num > 0){
        "$num is positive"
    }else if(num < 0){
        "$num is negative"
    }else{
        "$num is zero"
    }
    println(result)
}

Output :

10 is positive

Kotlin Nested if Expression

Let’s see an example of nested if expression.

fun main(args: Array<String>) {
    val num1 = 25
    val num2 = 20
    val num3 = 30
    val result = if (num1 > num2){

        val max = if(num1 > num3){
            num1
        }else{
            num3
        }
        "body of if "+max
    }else if(num2 > num3){
        "body of else if"+num2
    }else{
        "body of else "+num3
    }
    println("$result")
}

Output :

body of if 30

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