Kotlin Booleans

Kotlin Booleans

Very often, in programming, you will need a data type that can only have one of two values, like:

• YES / NO
• ON / OFF
• TRUE / FALSE

For this, Kotlin has a Boolean data type, which can take the values true or false.

Boolean Values

A boolean type can be declared with the Boolean keyword and can only take the values true or false:

val isKotlinFun: Boolean = true
val isFishTasty: Boolean = false
println(isKotlinFun)   // Outputs true
println(isFishTasty)   // Outputs false 

Just like you have learned with other data types in the previous chapters, the example above can also be written without specifying the type, as Kotlin is smart enough to understand that the variables are Booleans:

val isKotlinFun = true
val isFishTasty = false
println(isKotlinFun)   // Outputs true
println(isFishTasty)   // Outputs false 

Boolean Expression

A Boolean expression returns a Boolean value: true or false.

You can use a comparison operator, such as the greater than (>) operator to find out if an expression (or a variable) is true:

val x = 10
val y = 9
println(x > y) // Returns true, because 10 is greater than 9

Or even easier:

println(10 > 9) // Returns true, because 10 is greater than 9

In the examples below, we use the equal to (==) operator to evaluate an expression:

val x = 10;
println(x == 10); // Returns true, because the value of x is equal to 10

println(10 == 15); // Returns false, because 10 is not equal to 15