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How to check if a string is a valid email address in Kotlin

How to check if a string is a valid email address in Kotlin.

Here is a step-by-step tutorial on how to check if a string is a valid email address in Kotlin:

Step 1: Import the necessary classes​

import java.util.regex.Pattern

We will be using the Pattern class from the java.util.regex package to define and match the regular expression for validating the email address.

Step 2: Define the regular expression pattern​

val emailPattern = Pattern.compile(
    "[a-zA-Z0-9\\+\\.\\_\\%\\-\\+]{1,256}" +
    "\\@" +
    "[a-zA-Z0-9][a-zA-Z0-9\\-]{0,64}" +
    "(" +
    "\\." +
    "[a-zA-Z0-9][a-zA-Z0-9\\-]{0,25}" +
    ")+"
)

This regular expression pattern follows the typical structure of an email address and ensures that it contains valid characters in the local part and domain part, as well as the correct structure of the domain.

Step 3: Write a function to validate the email address​

fun isEmailValid(email: String): Boolean {
    val matcher = emailPattern.matcher(email)
    return matcher.matches()
}

This function takes an email address as input and uses the matcher object to check if it matches the defined pattern. If the email address matches the pattern, the function returns true; otherwise, it returns false.

Step 4: Test the function with different email addresses​

fun main() {
    val email1 = "test@example.com"
    val email2 = "invalid_email"
    val email3 = "user@domain"

    println("Email 1 is valid: ${isEmailValid(email1)}")
    println("Email 2 is valid: ${isEmailValid(email2)}")
    println("Email 3 is valid: ${isEmailValid(email3)}")
}

In this example, we test the isEmailValid function with three different email addresses. The program outputs whether each email address is valid or not.

That's it! You now have a working implementation to check if a string is a valid email address in Kotlin.