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Creating Custom Exceptions

Exception handling is an essential aspect of writing robust and error-resistant code. Kotlin, a modern programming language, provides a powerful mechanism for handling exceptions. In this post, we’ll delve into the concept of creating custom exceptions in Kotlin, allowing you to tailor error handling to suit the specific needs of your application.

What are Custom Exceptions?

Kotlin, like many other programming languages, allows developers to define their own exceptions. These custom exceptions extend the standard exception classes provided by the language and can be thrown when certain conditions are not met. Creating custom exceptions enables you to communicate application-specific errors effectively.

Creating a Basic Custom Exception

Let’s start by creating a simple custom exception. In Kotlin, this involves creating a new class that extends the Exception class. Here’s an example:

class CustomException(message: String) : Exception(message)

In this example, CustomException is a subclass of the built-in Exception class, and it takes a message as a parameter. The message is a human-readable description of the exception and can provide valuable information when debugging.

Throwing Custom Exceptions

Once you’ve defined your custom exception, you can throw it in your code when necessary. Consider the following example:

fun divide(a: Int, b: Int): Int {
if (b == 0) {
throw CustomException("Cannot divide by zero")
return a / b

In this function, a custom exception is thrown when attempting to divide by zero. This allows you to handle this specific error case in a way that makes sense for your application.

Handling Custom Exceptions

Handling custom exceptions is similar to handling standard exceptions in Kotlin. You can use try-catch blocks to catch and handle specific exceptions. Here’s an example:

fun main() {
try {
val result = divide(10, 0)
println("Result: $result")
} catch (e: CustomException) {
println("Error: ${e.message}")

In this example, the divide function is called with parameters that would normally result in a division by zero error. The custom exception is caught in the catch block, and a meaningful error message is printed.

Adding Custom Properties to Exceptions

Custom exceptions in Kotlin can also include additional properties to provide more context about the error. For instance, you might want to include an error code or other relevant information. Here’s an example:

class CustomException(val errorCode: Int, message: String) : Exception(message)

Now, when creating an instance of CustomException, you can provide an error code along with the message.