Intro to Regular Expressions (Pattern Matching)

In this lesson you will learn the basics of pattern matching with regular expressions in Kotlin so you can check whether text follows a given format. This is for anyone searching for "Kotlin regular expressions how to use".

A regular expression is a special notation that describes the shape of a string. You can specify a pattern such as "three digits, a hyphen, then four digits", check whether text matches it, and pull out the matching part. Kotlin provides the Regex class.

The sample code builds a phone-number-like pattern with Regex(...) and extracts the matching part with regex.find(text)?.value. As Regex("^\d+$").matches("12345") shows, the same class also simply answers whether the text matches.

A common stumbling block for beginners is learning what all the symbols mean. It looks like nothing but punctuation at first, but it is a powerful tool that pays off in practice, for example when validating email formats.

In real-world development, learning regular expressions once gives you a skill that transfers to most other programming languages.

📖 Reference code

fun main() {
    val text = "Phone: 090-1234-5678"
    val regex = Regex("\\d{3}-\\d{4}-\\d{4}")
    println(regex.find(text)?.value)
    println(Regex("^\\d+$").matches("12345"))
}

✍️ 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).