Method hashMapOf() in Kotlin

Question

Can anybody please give me Concrete example of hashMapOf() method and when should I use it?

If i do something like this:

val map2 : HashMap<String, String>  = hashMapOf()
    map2["ok"] = "yes"

It means to initialize map2 property I can use it.

But like other method in Kotlin for example:

val arr = arrayListOf<String>("1", "2", "3")

Is there any way I can use this method like above?

Answer 1

It's simple:

val map = hashMapOf("ok" to "yes", "cancel" to "no")

print(map) // >>> {ok=yes, cancel=no}

Method hashMapOf returns java.util.HashMap instance with the specified key-value pairs.

Under the hood:

/**
 * Creates a tuple of type [Pair] from this and [that].
 *
 * This can be useful for creating [Map] literals with less noise, for example:
 * @sample samples.collections.Maps.Instantiation.mapFromPairs
 */
public infix fun <A, B> A.to(that: B): Pair<A, B> = Pair(this, that)

Answer 2

Yes, you can. First example from kotlinlang.org:

val map: HashMap<Int, String> = hashMapOf(1 to "x", 2 to "y", -1 to "zz")
println(map) // {-1=zz, 1=x, 2=y}