Conditional (If, Else)

Kotlin Tutorial

Kotlin Classes

Conditional Statements (If..else)

So far, we learned Comparison Operators; Conditional Statements are all about them. They take decisions according to Boolean values; either true or false.

Note: Kotlin does not support ternary operators for conditions like ( condition ? then : else)

Kotlin got “if” as an expression which returns a value.

Syntax

				
					if (condition) {
   // code which executes if the condition is true
}

Note: “If” expression is in lowercase; uppercase “IF” will throw a compile time error

Normal usage of if..else:

Example:

				
					var a = 20

if (a > 30) {
   println("a is greater than 30")
} else {
   println("a is less than 30")
}

The code above outputs:

a is less than 30

Kotlin If as expression

				
					var a  = 20

result = if (a > 30) {
   "a is greater than 30"
} else {
   "a is less than 30"
}

println(result)

The code above outputs:

a is less than 30

“else” is mandatory if you are using if as an expression.

Let’s see another example:

Change the value of variable bulb to false and RUN the code again you will see the different output.

				
					var bulb : Boolean = true

var result = if (bulb == true) {
   "Bulb is on"
} else {
   "Bulb is off"
}
println(result)

The following code outputs:

Bulb is on

Note: You can omit the curly braces {} when “if” has only one statement. .

				
					if (bulb == true) "bulb is on" else "bulb is off"

This is quite similar to the ternary operator in Java; but Kotin does not support it.

If..else Ladder

You can take multiple decisions using if..else Or we can say (ladder if..else..if..else), for example

				
					var number = 20

if (number < 0) {
   println("$number is negative")
} else if (number > 0) {
   println("$number is positive")
} else {
   println("$number is Zero")
}

The code above outputs:

				
					20 is positive

Or you also can do

				
					var number = 20

var result = if (number < 0) {
   "$number is negative"
} else if (number > 0) {
   "$number is positive"
} else {
   "$number is Zero"
}

print(result)

Output will be the same.

In the above example the 2nd condition is true: change the number value to 0 and RUN it