Kotlin If Expression

Kotlin if 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.

• if-else expression
• if-else if-else ladder expression
• 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) {
    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.

For example:
fun main(args: Array) {
    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 Expression
Let's see an example of if-else if-else ladder expression.

fun main(args: Array) {
    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) {
    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