try/catch

Learn to catch errors with try/catch.

try/catch: catching errors

A piece of code may throw an error; a try block wraps that code, catch catches the error. The program then continues without crashing.

try {
    val x = 10 / 0
} catch (e: ArithmeticException) {
    println("Error: ${e.message}")
}

If the code inside try fails, control jumps to catch. The caught object is bound to e; e.message carries the error text. Catching the right exception type prevents unexpected failures.

Specific exception types

Each error type points to a different situation. The most common: ArithmeticException, NumberFormatException, NullPointerException, IndexOutOfBoundsException.

try {
    val n = "abc".toInt()
} catch (e: NumberFormatException) {
    println("Not a number")
}

The right type matters for handling the error well. For unknown errors you can catch Exception; but specific types give clearer information. A wrong type lets the error slip past.

Exercise Wrap division in try/catch

Inside a try block write val x = 10 / 0. Catch ArithmeticException and print "Error" with println.

Show example solution

fun main() {
    try {
        val x = 10 / 0
    } catch (e: ArithmeticException) {
        println("Error")
    }
}

Test yourself

What does the catch block do?
- It throws an error
- It must ignore the error
- It repeats the error
- It catches the error
Show answer

It catches the error — catch catches the error raised inside try.

Fill in the blank: write catch

try {
    val x = 10 / 0
} ____ (e: ArithmeticException) {
    println("Error")
}

Show answer

try {
    val x = 10 / 0
} catch (e: ArithmeticException) {
    println("Error")
}

Match exception to scenario

ArithmeticException

Division error
NumberFormatException

Conversion error
IndexOutOfBoundsException

Array bound
NullPointerException

Null access

Next lesson: throw

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