Throw as an expression in Kotlin - Mini Project: Build & Apply

Throw as an expression in Kotlin

📖 Scenario: You are building a simple Kotlin program that checks user input for a valid age. If the age is invalid, the program should stop and show an error.

🎯 Goal: Learn how to use throw as an expression in Kotlin to handle errors in a clean and concise way.

📋 What You'll Learn

Create a variable with a user age value

Create a minimum age limit variable

Use throw as an expression to check the age

Print a success message if the age is valid

💡 Why This Matters

🌍 Real World

Throwing exceptions as expressions helps write cleaner Kotlin code for input validation and error handling.

💼 Career

Understanding throw as an expression is important for Kotlin developers to write concise and safe code in apps and backend services.

1

Create the user age variable

Create an Int variable called userAge and set it to 20.

Kotlin

# Create an Int variable called userAge and set it to 20
# Your code here

Need a hint?

Use val to create a variable that does not change.

2

Create the minimum age limit variable

Create an Int variable called minAge and set it to 18.

Kotlin

val userAge: Int = 20
# Create an Int variable called minAge and set it to 18
# Your code here

Need a hint?

Use val to create a constant variable.

3

Use throw as an expression to check age

Create a variable called validAge that uses an if expression to check if userAge is greater than or equal to minAge. If true, assign true. Otherwise, use throw IllegalArgumentException("Age is below minimum") as the else expression.

Kotlin

val userAge: Int = 20
val minAge: Int = 18
# Create a variable validAge using if expression with throw as else
# Your code here

Need a hint?

Use throw inside the else part of the if expression.

4

Print the success message

Write a println statement to print "User age is valid".

Kotlin

val userAge: Int = 20
val minAge: Int = 18
val validAge: Boolean = if (userAge >= minAge) true else throw IllegalArgumentException("Age is below minimum")
# Print "User age is valid" below
# Your code here

Need a hint?

Use println("User age is valid") to show the message.