Type Conversion

fun main() {
    val wholeNumber: Int = 10
    val decimalNumber: Double = wholeNumber.toDouble()
    println("Int: $wholeNumber, Double: $decimalNumber")
}

fun main() {
    val price: Double = 19.99
    val roundedDown: Int = price.toInt()
    println("Price: $price, as Int: $roundedDown")
}

fun main() {
    val text = "42"
    val number = text.toInt()
    println("Parsed number: ${number + 8}")
}

fun main() {
    val goodInput = "123"
    val badInput = "abc"
    println("Good: ${goodInput.toIntOrNull()}")
    println("Bad: ${badInput.toIntOrNull()}")
}

1. Expecting implicit widening conversions like in Java/C, such as assigning an Int directly to a Double variable; Kotlin requires an explicit toDouble() call.
2. Using as for numeric conversions instead of the proper toInt()/toDouble() functions, which is meant for type casting, not conversion.
3. Calling toInt() on a non-numeric string and not handling the NumberFormatException that results.

• Kotlin never performs implicit numeric conversions; every conversion between types like Int and Double must be explicit.
• Conversion functions like toInt(), toDouble(), toLong(), and toString() convert between numeric types and strings.
• Converting a non-numeric string with toInt() throws a NumberFormatException at runtime.
• toIntOrNull() and similar OrNull variants return null instead of throwing when conversion fails.