Kotlin Map isNullOrEmpty()
Syntax & Examples

Syntax of Map.isNullOrEmpty()

The syntax of Map.isNullOrEmpty() extension function is:

fun <K, V> Map<out K, V>?.isNullOrEmpty(): Boolean

This isNullOrEmpty() extension function of Map returns true if this nullable map is either null or empty.

✐ Examples

1 Check if a non-empty map is null or empty

In this example,

We create a non-empty map named map1.
We use the isNullOrEmpty function on map1.
Since map1 is non-empty, the function returns false.
We print the result to standard output.

Kotlin Program

fun main(args: Array<String>) {
    val map1 = mapOf("key1" to "value1", "key2" to "value2")
    val result1 = map1.isNullOrEmpty()
    println(result1)
}

Output

false

2 Check if an empty map is null or empty

In this example,

We create an empty map named map2.
We use the isNullOrEmpty function on map2.
Since map2 is empty, the function returns true.
We print the result to standard output.

Kotlin Program

fun main(args: Array<String>) {
    val map2 = emptyMap<String, Int>()
    val result2 = map2.isNullOrEmpty()
    println(result2)
}

Output

true

3 Check if a nullable map is null or empty

In this example,

We declare a nullable map map3 and assign it a value of null.
We use the isNullOrEmpty function on map3.
Since map3 is null, the function returns true.
We print the result to standard output.

Kotlin Program

fun main(args: Array<String>) {
    val map3: Map<String, String>? = null
    val result3 = map3.isNullOrEmpty()
    println(result3)
}

Output

true

Summary

In this Kotlin tutorial, we learned about isNullOrEmpty() extension function of Map: the syntax and few working examples with output and detailed explanation for each example.