Normalizing Strings (trim, Unifying Case)

In this lesson you will learn how to normalize strings in Kotlin, so inconsistent formatting can still be compared. This is for anyone searching for "Kotlin string normalization".

Text entered by a user tends to carry stray leading or trailing spaces and inconsistent capitalisation. Stripping the spaces with .trim() and unifying the case with .lowercase() is called normalization.

The sample code runs s.trim().lowercase() inside a normalize() function, removing surrounding whitespace and then folding to lower case. You can see two strings that look different compare as equal once normalized.

A common stumbling block for beginners is comparing strings without doing this first. Two values that look identical to a human can still come back as false, and the cause is hard to spot.

In real-world development normalization is a basic technique you cannot do without in input validation and login handling.

📖 Reference code

fun normalize(s: String): String = s.trim().lowercase()

fun main() {
    println(normalize("  Hello World  ") == normalize("hello world"))
    println(normalize("  Hello World  "))
}

✍️ Your code

Type your code, then press "Run"

🧪 This site can't compile or run Kotlin directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).