Kotools Types/kotools.types.collection/toNotEmptyMapOrThrow

toNotEmptyMapOrThrow

@ExperimentalSinceKotoolsTypes(version = "4.3.1")

fun <K, V> Map<K, V>.toNotEmptyMapOrThrow(): NotEmptyMap<K, V>

Returns a NotEmptyMap containing all the entries of this map, or throws an IllegalArgumentException if this map is empty.

var map: Map<Char, Int> = mapOf('a' to 1, 'b' to 2)
var result: NotEmptyMap<Char, Int> = map.toNotEmptyMapOrThrow()
println(result) // {a=1, b=2}

map = emptyMap()
map.toNotEmptyMapOrThrow() // IllegalArgumentException

Please note that changes made to the original map will not be reflected on the resulting NotEmptyMap.

val original: MutableMap<Char, Int> = mutableMapOf('a' to 1, 'b' to 2)
val notEmptyMap: NotEmptyMap<Char, Int> = original.toNotEmptyMapOrThrow()
println(original) // {a=1, b=2}
println(notEmptyMap) // {a=1, b=2}

original.clear()
println(original) // {}
println(notEmptyMap) // {a=1, b=2}

You can use the toNotEmptyMapOrNull function for returning null instead of throwing an IllegalArgumentException when this map is empty.