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: There are several ways to initialize an empty list as discussed below: 1. listOf() function. In this tutorial, we are going to learn about Kotlin ArrayList with the help of examples. listOfNotNull() returns an immutable list excluding all null elements. Entries of the map are iterated in the order they were specified. It is a modifiable collection. It inherits form Collection class. This article explores different ways to initialize an empty List in Kotlin. Contribute to JetBrains/kotlin development by creating an account on GitHub. The methods of MutableList interface supports both read and write functionalities. https://www.baeldung.com/kotlin/initialize-empty-mutable-collections */ @SinceKotlin(" 1.4 ") MutableList interface is mutable in nature. Able to define a Kotlin class, create an object instance from it, and access its properties and methods. 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. 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.. If you need an immutable empty list instance, you can use listOf() function as shown below. The kotlin functions sort, sortBy etc. 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? List: listOf; Map: mapOf; Set: setOf; And mutable collections. Edit Page Constructing Collections Constructing from elements. 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. In this tutorial, we are going to learn about Kotlin mutableMapOf collection with the help of examples. The MutableList interface also inherits the Collection interface. Immutable. Last element in list: Kotlin Is list empty: false Sublist from index 1 to 3 [Study, tonight] Kotlin Mutable List. If the list is not null and not empty, I want to do something, otherwise I want to do something else. It creates a MutableList implementation which provides a dynamic array size as its backing storage. This creates an immutable list, similar to Arrays.asList in Java. all sort the items in the list itself. Mutable lists are dynamic in nature. We have two types of collections in Kotlin. Kotlin MutableList (mutableListOf()) Kotlin MutableList is an interface and generic collection of elements. ... or returns `null` if this list is empty. From the documentation of sort: Sorts the array in-place according to the natural order of its elements. Mutable lists (MutableList) Mutable lists can have elements added or removed. ... * Removes the first element from this mutable list and returns that removed element, or throws [NoSuchElementException] if this list is empty. In Kotlin, mutableListOf() method is used to instantiate MutableList Interface. MutableList class is used to create mutable lists in which the elements can be added or removed. It holds the data as key and value. If multiple pairs have the same key, the resulting map will contain the value from the last of those pairs. Mutable lists are created using MutableList interface. ArrayList is a mutable collection. A key is a unique identifier for the value. 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