Custom Exceptions | Error Handling

Introduction

In Scala, exceptions are used to handle errors and other exceptional events. While Scala provides a rich set of built-in exceptions, there are times when you may need to define your own custom exceptions to handle specific error scenarios that are unique to your application. This tutorial will guide you through creating and using custom exceptions in Scala.

Creating a Custom Exception

To create a custom exception in Scala, you need to extend the Exception class or one of its subclasses. Below is a simple example where we create a custom exception called InvalidInputException to handle invalid user inputs.

Example: Custom Exception Definition

class InvalidInputException(message: String) extends Exception(message)

This class takes a string message as a parameter and passes it to the superclass constructor.

Using Custom Exceptions

Once you have defined a custom exception, you can use it in your code to throw exceptions under certain conditions. Below is an example of a method that checks user input and throws an InvalidInputException if the input is not valid.

Example: Throwing a Custom Exception

def validateInput(input: Int): Unit = {
    if (input < 0) {
        throw new InvalidInputException("Input must be a non-negative integer.")
    } else {
        println("Input is valid.")
    }
}

In this method, if the input is negative, an InvalidInputException is thrown with a descriptive message.

Handling Custom Exceptions

To handle custom exceptions, you can use a try-catch block. Below is an example of how to handle the InvalidInputException when calling the validateInput function.

Example: Catching a Custom Exception

try {
    validateInput(-5)
} catch {
    case e: InvalidInputException => println(s"Caught an exception: ${e.getMessage}")
}

In this example, the invalid input (-5) triggers the exception, which is then caught and handled in the catch block, printing a relevant message to the console.

Conclusion

Custom exceptions are a powerful feature in Scala that allow you to handle specific error scenarios in a way that is meaningful for your applications. By defining your own exceptions, you can improve the error handling capabilities of your code, making it more robust and easier to maintain. This tutorial provided a comprehensive overview of how to create, use, and handle custom exceptions in Scala. You can now implement your own custom exceptions based on your application's requirements.

Custom Exceptions in Scala