1. What Is an Exception?

[THEORY]

[PREDICT]

Read the code carefully before you run it.

prediction.kt

fun registerOrder(quantity: Int, stock: Int) {
    if (quantity > stock) {
        throw IllegalStateException("Not enough stock: $quantity requested, $stock available")
    }
    println("Order ($quantity units) registered successfully")
}

fun main() {
    println("Start")
    registerOrder(15, 10)
    println("End")
}

What does the program output? Is "Ende" still printed?

[TASK]

Write a function registerOrder(quantity: Int, stock: Int). If quantity is greater than stock, throw an IllegalStateException with the message "Not enough stock: $quantity requested, $stock available". Otherwise print "Order ($quantity units) registered successfully". Call the function in main() with quantity = 15 and stock = 10 — the program should abort with a stack trace. Catching is the topic of the next lesson; here it is only about throw.

task.kt

fun registerOrder(quantity: Int, stock: Int) { // TODO: throw an IllegalStateException when there is not enough stock // TODO: otherwise print the success message } fun main() { registerOrder(15, 10) }

Before you get a hint: what have you tried, and where exactly are you stuck?

[COMPREHENSION CHECK]

1. According to common convention, what should you NOT use exceptions for?

To pass an error up the call chain until it reaches a place that can handle it To keep error handling in catch blocks separate from the normal program logic To model an expected case like 'user not found' as normal control flow To distinguish different kinds of errors by the exception type that was thrown

2. Throwable is the base class of the Kotlin exception hierarchy. Which two direct subclasses does it have?

Exception and Error, for handleable problems and for serious system failures Exception and RuntimeException, for checked problems and for unchecked problems CheckedException and UncheckedException, the same two classes that Java provides RuntimeException and Error, for programming mistakes and for serious system failures