Kotlin Booleans

Declaring Boolean Values

A Boolean variable in Kotlin can hold only true or false, with no implicit conversion from numbers or strings, unlike some other languages. This strictness prevents an entire category of accidental bugs.

fun main() {
    val isRaining = true
    val isWeekend = false

    println("Is it raining? $isRaining")
    println("Is it the weekend? $isWeekend")
}

Booleans from Comparisons

Most Boolean values in real programs come from evaluating an expression rather than being typed literally. Any comparison or logical expression automatically produces a Boolean result that can be stored, printed, or used directly in a condition.

fun main() {
    val temperature = 38
    val isHot = temperature > 30
    val isFreezing = temperature < 0

    println("Is it hot? $isHot")
    println("Is it freezing? $isFreezing")

    if (isHot) {
        println("Remember to stay hydrated!")
    }
}

Booleans in Control Flow

• Conditions inside if / else branches
• Loop conditions in while and do-while loops
• Guard clauses that return early from a function
• Flags that track state, such as isLoggedIn or hasPermission
• Return types of predicate functions like isValid(input: String): Boolean

fun isEven(number: Int): Boolean {
    return number % 2 == 0
}

fun main() {
    val values = listOf(4, 7, 10, 13)

    for (value in values) {
        val result = isEven(value)
        println("$value is even: $result")
    }
}