Elvis operator (?:) for default values in Kotlin - Mini Project: Build & Apply

Using the Elvis Operator (?:) for Default Values in Kotlin

📖 Scenario: Imagine you are building a simple app that greets users. Sometimes, the user's name might not be provided, so you want to use a default greeting instead.

🎯 Goal: You will create a Kotlin program that uses the Elvis operator ?: to provide a default greeting when the user's name is missing.

📋 What You'll Learn

Create a nullable variable for the user's name

Create a default greeting string

Use the Elvis operator ?: to assign a greeting message

Print the final greeting message

💡 Why This Matters

🌍 Real World

Many apps need to handle missing or optional information gracefully, like showing a default name when the user does not provide one.

💼 Career

Understanding how to use the Elvis operator helps you write safer Kotlin code that avoids crashes from null values.

1

Create a nullable variable for the user's name

Create a nullable String variable called userName and set it to null.

Kotlin

// Create a nullable String variable userName and set it to null
// Your code here

Need a hint?

Use String? to make the variable nullable and assign null to it.

2

Create a default greeting string

Create a String variable called defaultGreeting and set it to "Hello, Guest!".

Kotlin

val userName: String? = null
// Create a String variable defaultGreeting with value "Hello, Guest!"
// Your code here

Need a hint?

Just assign the string "Hello, Guest!" to the variable defaultGreeting.

3

Use the Elvis operator to assign a greeting message

Create a String variable called greeting that uses the Elvis operator ?: to assign userName if it is not null, or defaultGreeting if it is null.

Kotlin

val userName: String? = null
val defaultGreeting = "Hello, Guest!"
// Use the Elvis operator ?: to assign greeting
// Your code here

Need a hint?

Use userName ?: defaultGreeting to assign greeting.

4

Print the final greeting message

Write a println statement to print the value of greeting.

Kotlin

val userName: String? = null
val defaultGreeting = "Hello, Guest!"
val greeting = userName ?: defaultGreeting
// Print the greeting
// Your code here

Need a hint?

Use println(greeting) to show the greeting on the screen.