How do I initialize Kotlin s MutableList to empty MutableList

Question

Seems so simple  but  how do I initialize Kotlin s MutableList to empty MutableList   I could hack it this way  but I m sure there is something easier available   var pusta  List lt Kolory gt    emptyList   var cos  MutableList lt Kolory gt    pusta toArrayList

User · Answer

I do like below to     var book  MutableList lt Books gt    mutableListOf         Returns a new  MutableList  with the given elements      public fun  lt T gt  mutableListOf vararg elements  T   MutableList lt T gt        if  elements size    0  ArrayList   else ArrayList ArrayAsCollection elements  isVarargs   true

User · Answer

You can simply write   val mutableList   mutableListOf lt Kolory gt      This is the most idiomatic way   Alternative ways are  val mutableList   MutableList lt Kolory gt    arrayListOf     or  val mutableList   MutableList lt Kolory gt    ArrayList     This is exploiting the fact that java types like ArrayList are implicitly implementing the type MutableList via a compiler trick

User · Answer

Various forms depending on type of List  for Array List   val myList   mutableListOf lt Kolory gt        or more specifically use the helper for a specific list type val myList   arrayListOf lt Kolory gt      For LinkedList   val myList   linkedListOf lt Kolory gt       same as val myList  MutableList lt Kolory gt    linkedListOf     For other list types  will be assumed Mutable if you construct them directly   val myList   ArrayList lt Kolory gt       or val myList   LinkedList lt Kolory gt      This holds true for anything implementing the List interface  i e  other collections libraries      No need to repeat the type on the left side if the list is already Mutable   Or only if you want to treat them as read-only  for example   val myList  List lt Kolory gt    ArrayList

[kotlin] How do I initialize Kotlin's MutableList to empty MutableList?

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