Map Element Access

When applied to a map, [] operator returns the value corresponding to the given key, or null if there is no such key in the map.

getValue function returns an existing value corresponding to the given key or throws an exception if the key wasn't found. For maps created with withDefault, getValue returns the default value instead of throwing an exception.

fun main(args: Array<String>) {

    val map = mapOf("key" to 42)
    
    val value1 = map["key"]                                     // 1
    val value2 = map["key2"]                                    // 2

    val value3: Int = map.getValue("key")                       // 1

    val mapWithDefault = map.withDefault { k -> k.length }
    val value4 = mapWithDefault.getValue("key2")                // 3
    
    try {
        map.getValue("anotherKey")                              // 4
    } catch (e: NoSuchElementException) {
        println("Message: $e")
    }


    println("value1 is $value1")
    println("value2 is $value2")
    println("value3 is $value3")
    println("value4 is $value4")
}

1. Returns 42 because it's the value corresponding to the key "key".
2. Returns null because "key2" is not in the map.
3. Returns the default value because "key2" is absent. For this key it's 4.
4. Throws NoSuchElementException because "anotherKey" is not in the map.