How to Check if String is Empty in Kotlin

In Kotlin, you can check if a string is empty using the isEmpty() function or by comparing it to an empty string "". For example, myString.isEmpty() returns true if the string has no characters.

Syntax

The main way to check if a string is empty in Kotlin is by using the isEmpty() function. It returns true if the string has zero characters.

You can also compare the string directly to an empty string "" using ==.

kotlin

val myString = ""
val isEmpty = myString.isEmpty()  // true
val isEmptyCompare = (myString == "")  // true

Example

This example shows how to check if a string is empty using isEmpty() and prints a message accordingly.

kotlin

fun main() {
    val emptyString = ""
    val nonEmptyString = "Hello"

    if (emptyString.isEmpty()) {
        println("The string is empty.")
    } else {
        println("The string is not empty.")
    }

    if (nonEmptyString.isEmpty()) {
        println("The string is empty.")
    } else {
        println("The string is not empty.")
    }
}

Output

The string is empty.
The string is not empty.

Common Pitfalls

A common mistake is to check if a string is empty by comparing it to null instead of checking if it has zero characters. Remember, isEmpty() only checks for empty strings, not null.

To safely check for both null and empty strings, use isNullOrEmpty().

kotlin

fun main() {
    val nullableString: String? = null

    // Wrong: This will cause an error if string is null
    // println(nullableString.isEmpty())

    // Right: Use isNullOrEmpty to check for null or empty
    if (nullableString.isNullOrEmpty()) {
        println("String is null or empty.")
    } else {
        println("String has content.")
    }
}

Output

String is null or empty.

Quick Reference

Method	Description	Returns
isEmpty()	Checks if string has zero characters	Boolean (true if empty)
== ""	Compares string to empty string	Boolean (true if empty)
isNullOrEmpty()	Checks if string is null or empty	Boolean (true if null or empty)

Key Takeaways

Use isEmpty() to check if a string has no characters.

Comparing a string to "" also works to check emptiness.

Use isNullOrEmpty() to safely check for null or empty strings.

Avoid calling isEmpty() on nullable strings without a null check.

Empty string means zero characters, different from null which means no value.