all sort the items in the list itself. The methods of MutableList interface supports both read and write functionalities. Mutable lists are created using MutableList interface. ... or returns `null` if this list is empty. */ @SinceKotlin(" 1.4 ") This article explores different ways to initialize an empty List in Kotlin. I came up with following solution: when { activities != null && !activities.empty -> doSomething else -> doSomethingElse } Is there a more idiomatic way to do this in Kotlin? Kotlin MutableList (mutableListOf()) Kotlin MutableList is an interface and generic collection of elements. Returns a new MutableMap with the specified contents, given as a list of pairs where the first component is the key and the second is the value.. ... * Removes the first element from this mutable list and returns that removed element, or throws [NoSuchElementException] if this list is empty. This creates an immutable list, similar to Arrays.asList in Java. It inherits form Collection class. There are several ways to initialize an empty list as discussed below: 1. listOf() function. Contribute to JetBrains/kotlin development by creating an account on GitHub. The method mutableListOf() returns an instance of MutableList Interface and takes the array of a particular type or mixed (depends on the type of MutableList instance) elements or it can be null also. From the documentation of sort: Sorts the array in-place according to the natural order of its elements. Immutable. Mutable lists (MutableList) Mutable lists can have elements added or removed. If you don't want to sort the elements in-place but rather return a sorted list (your base doesn't need to be a MutableList), you can use sorted, sortedBy etc: Entries of the map are iterated in the order they were specified. A key is a unique identifier for the value. It is a modifiable collection. MutableList interface is mutable in nature. listOfNotNull() returns an immutable list excluding all null elements. The MutableList interface also inherits the Collection interface. MutableList class is used to create mutable lists in which the elements can be added or removed. It creates a MutableList implementation which provides a dynamic array size as its backing storage. https://www.baeldung.com/kotlin/initialize-empty-mutable-collections In this tutorial, we are going to learn about Kotlin mutableMapOf collection with the help of examples. In this tutorial, we are going to learn about Kotlin ArrayList with the help of examples. The most common way to create a collection is with the standard library functions listOf(), setOf(), mutableListOf(), mutableSetOf().If you provide a comma-separated list of collection elements as arguments, the compiler detects the element type automatically. If you need an immutable empty list instance, you can use listOf() function as shown below. It holds the data as key and value. List: listOf; Map: mapOf; Set: setOf; And mutable collections. The kotlin functions sort, sortBy etc. If the list is not null and not empty, I want to do something, otherwise I want to do something else. Last element in list: Kotlin Is list empty: false Sublist from index 1 to 3 [Study, tonight] Kotlin Mutable List. If multiple pairs have the same key, the resulting map will contain the value from the last of those pairs. In Kotlin, mutableListOf() method is used to instantiate MutableList Interface. As frogcoder states in a comment, emptyList() does the same, but naturally returns an empty list. Familiar with basic Kotlin programming concepts from Unit 1 of the Android Basics in Kotlin course: the main() function, functions arguments and return values, variables, data types and operations, as well as control flow statements. Edit Page Constructing Collections Constructing from elements. Mutable lists are dynamic in nature. We have two types of collections in Kotlin. 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