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