String to number conversion in Kotlin - Mini Project: Build & Apply

String to number conversion

📖 Scenario: You are building a simple calculator app that takes numbers as text input from users. To perform calculations, you need to convert these text inputs into numbers.

🎯 Goal: Learn how to convert strings into numbers in Kotlin using safe methods to avoid errors.

📋 What You'll Learn

Create a string variable with a number as text

Create a variable to hold the converted number

Convert the string to an integer using toIntOrNull()

Print the converted number or a message if conversion fails

💡 Why This Matters

🌍 Real World

Converting text input to numbers is common in apps like calculators, forms, and data processing tools.

💼 Career

Understanding safe string to number conversion helps prevent app crashes and improves user experience in software development.

1

Create a string variable with a number

Create a string variable called numberText and set it to the value "123".

Kotlin

// Create a string variable called numberText and set it to "123"
// Your code here

Need a hint?

Use val to create a variable and assign the string "123" to numberText.

2

Create a variable to hold the converted number

Create a variable called number and set it to null initially. This will hold the converted integer later.

Kotlin

val numberText = "123"
// Create a variable called number and set it to null
// Your code here

Need a hint?

Use var because the value will change later. Use Int? to allow null.

3

Convert the string to an integer safely

Convert numberText to an integer using toIntOrNull() and assign it to number.

Kotlin

val numberText = "123"
var number: Int? = null
// Convert numberText to Int using toIntOrNull() and assign to number
// Your code here

Need a hint?

Use toIntOrNull() to safely convert the string to an integer without crashing if the string is invalid.

4

Print the converted number or a message

Write a println statement that prints number if it is not null, or prints "Conversion failed" if it is null.

Kotlin

val numberText = "123"
var number: Int? = null
number = numberText.toIntOrNull()
// Print number if not null, else print "Conversion failed"
// Your code here

Need a hint?

Use the Elvis operator ?: to print a default message if number is null.