/* Author: LukArToDo Created: 21.may 2018 Description: How to initialize List and MutableList (with and without elements) ? */ fun main(LukArToDo: Array) { /* Kotlin has mutable and immutable collections (lists, sets, maps, etc) where immutable collections do not allow for any changes (size of collections, value of elements, etc). Mutable collections allow all these changes. So, when defining collections, we must take care of whether it is immutable or mutable collections. */ /* 👉 List (MutableList): We differentiate three ways to define the collection List (or MutableList): 1. List is empty: - we use mutableListOf() and for immutable list: listOf() or emptyList(). - it is necessary to specify the type (String,Int,Double, etc.) when defining the list We can do this on two ways: a) val list : List = listOf() b) val list = listOf() */ val list: MutableList = mutableListOf() list.add("add Hello") println(list) val list1= mutableListOf() list1.add("add World") println(list1) /* 2. List not empty, we already know elements of list - we can specify type of list, but is not necessary because the compiler automatically determines the type of list based on the type of elements in the list. - so, we can define a list of known elements in three ways: a) val list : List = listOf(1,2,3) b) val list = listOf(1,2,3) c) val list = listOf(1,2,3) */ val listInt=mutableListOf(1,2,3) listInt.add(4) println(listInt) /* 3. List is not empty, we know the size of list and need to fill list - we can specify the type of list, but it is not necessary because we already defined the list type that we assign to our list. - so, we can do this on two ways: a) val list = List (size,{fill using expression or value}) b) val list : List = List (size,{fill using expression or value}) */ // Initialize list with size=4 and fill list with number 2 val listInt1 = List(4,{2}) // listInt1.add(5) // not allowed because Lists are immutable collections // listInt1.remove(2) // not alowed because Lists are immutable collections println(listInt1) // 2,2,2,2 // Initialize list with size=4 and fill list with first 4 even numbers val listInt2 = MutableList (4,{it*2}) // 'it' is index of list = 0,1,2... println(listInt2) // 0,2,4,6 // Initialize nullable list () with size=4 and fill list with null val listNull = List (4,{null}) println(listNull) /* Conclusion: - we use: List to specify type of list: val list : List = ... or fun function(list: List){} - List(size, {value}) or listOf(a,b,c) or listOf(a,b,c) are list with elements which we assign to our list and on that way we define type of our list (takes the type of assigned list or the type of element in the list that we assign) - emptyList() or listOf() or mutableListOf() are empty lists and in that case is necessary to define type of our list (because there are no elements in the list on which the compiler will specify type of list). We can use: val list : List = listOf() or shorter: val list = listOf() */ }

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