Non-nullable types by default in Kotlin - Mini Project: Build & Apply

Non-nullable types by default

📖 Scenario: You are creating a simple Kotlin program to store and display a person's name and age. Kotlin treats types as non-nullable by default, which means variables cannot hold null unless explicitly allowed.

🎯 Goal: Build a Kotlin program that defines a non-nullable name variable and a non-nullable age variable, then prints them.

📋 What You'll Learn

Create a non-nullable name variable of type String with the value "Alice".

Create a non-nullable age variable of type Int with the value 30.

Print the name and age variables in the format: Name: Alice, Age: 30.

💡 Why This Matters

🌍 Real World

Non-nullable types help prevent errors by ensuring variables always have valid values, which is important in apps that handle user data.

💼 Career

Understanding Kotlin's type system is essential for Android developers and anyone working with Kotlin to write safe and reliable code.

1

Create non-nullable variables

Create a non-nullable variable called name of type String and set it to "Alice".

Kotlin

# Your code here

Need a hint?

Use val to declare a read-only variable and specify the type String without a question mark.

2

Add a non-nullable age variable

Add a non-nullable variable called age of type Int and set it to 30 below the name variable.

Kotlin

val name: String = "Alice"
# Your code here

Need a hint?

Remember to declare age as Int without a question mark to keep it non-nullable.

3

Create a message string

Create a variable called message of type String that uses an f-string (string template) to combine name and age in the format: Name: Alice, Age: 30.

Kotlin

val name: String = "Alice"
val age: Int = 30
# Your code here

Need a hint?

Use Kotlin string templates with $variableName inside double quotes.

4

Print the message

Print the message variable using println.

Kotlin

val name: String = "Alice"
val age: Int = 30
val message: String = "Name: $name, Age: $age"
# Your code here

Need a hint?

Use println(message) to display the message on the screen.