Finally block behavior in Kotlin

Introduction

The finally block lets you run code that must happen no matter what, like cleaning up or closing files.

You open a file and want to make sure it closes even if an error happens.

You start a network connection and want to close it no matter what.

You allocate resources and want to release them safely after use.

You want to print a message after trying some code, whether it worked or failed.

Syntax

Kotlin

try {
    // code that might throw an exception
} catch (e: Exception) {
    // code to handle the exception
} finally {
    // code that always runs
}

The finally block runs after try and catch, no matter what.

If there is a return statement in try or catch, finally still runs before returning.

Examples

This runs the try code and then always runs the finally block.

Kotlin

try {
    println("Trying something")
} finally {
    println("Always runs")
}

Even if an error happens and is caught, the finally block runs.

Kotlin

try {
    throw Exception("Oops")
} catch (e: Exception) {
    println("Caught: ${e.message}")
} finally {
    println("Cleanup")
}

The finally block runs before the function returns a value.

Kotlin

fun test(): String {
    try {
        return "From try"
    } finally {
        println("Finally runs before return")
    }
}

println(test())

Sample Program

This program tries to divide by zero, which causes an error. The catch block handles it, and the finally block runs no matter what. Then the program continues.

Kotlin

fun main() {
    try {
        println("Start try")
        val result = 10 / 0  // This causes an exception
        println("Result: $result")
    } catch (e: ArithmeticException) {
        println("Caught exception: ${e.message}")
    } finally {
        println("This always runs")
    }
    println("Program continues")
}

Important Notes

Use finally to keep your program safe by cleaning up resources.

If finally has a return statement, it can override returns from try or catch. Avoid this to prevent confusion.

Summary

The finally block always runs after try and catch.

It is useful for cleanup tasks like closing files or releasing resources.

Even if an exception happens or a return occurs, finally runs before the method exits.