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Hi all. How can I create a List with initial capacity in Kotlin similar to Java? It seems the mutableListOf method only has elements parameter. 

dineshbob: `MutableList&lt;String&gt;(n, {""})`

Thanks Daniil. And it looks like the list has to be initialized inside the lamda itself, right? 

Not sure what you meant by initializing, here are the docs: <http://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/-mutable-list.html>

You would have to use the ArrayList constructor: `val list = ArrayList(size)`

I think the reason is because you can't make an assumption about what implementation mutableListOf gives you

E.g if it gives you a linked list which doesn't have a size initialiser

<@U28KM12LE> `MutableList`function  was added in 1.1 and works the same as `ArrayList`

My point is that the name MutableList just indicates "a list, that is mutable". If they wanted to change the underlying implementation in the future they could do

Although `MutableList&lt;String&gt;(n, {""})` will work fine - <@U5SBA6PPY> it's just initialising the first n as "", you can still mutate it after initialisation 

Thanks <@U28KM12LE> <@U0BHS1Y07> . If the ArrayList is created with an initial size, we can just call add() to add the elements. But if we create `MutableList&lt;String&gt;(n, {""}` then the List is initialized with empty strings. If we call add() to add the elements now, they are added after the empty strings. I see that's one big difference.

So is it ok to use the Java's `ArrayList(size)` directly in the Kotlin world? I thought that's not advised in Kotlin.

<@U5SBA6PPY> i don't think it is a bad practice. You could instantiate an ArrayList without any issue :wink:

Kotlin has it's own ArrayList that implements MutableList: <https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/-array-list/index.html> 

whoa. looks like there are two ArrayList. One for JVM which is type alias to Java's ArrayList, and another one for JS which implements MutableList

Oh I didn't notice that! So on JVM it doesn't implement MutableList?

In this document they say to use the methods such as mutableListOf to create the Lists: <https://kotlinlang.org/docs/reference/collections.html> <@U5R5E1C9F>

Yes, using MutableList should be the default when you need a mutable list

But since you seem to specifically want to use an ArrayList type structure where you specify an initial capacity of the underlying array, using the a specific ArrayList is fine 

Okay. that makes sense. Thanks :slightly_smiling_face:

&gt;on JVM it doesn't implement MutableList?
It does. The type hierarchy does not depend on the target platform. The types are mapped. Details: <http://kotlinlang.org/docs/reference/java-interop.html#mapped-types>