Kotlin mutableSetOf() method
Kotlin Set interface is a generic unordered collection of elements and it does not contain duplicate elements. Kotlin supports two types of sets mutable and immutable.
setOf() is immutable means it supports only read-only functionalities and mutableSetOf() is mutable means it supports read and write both functionality.
Syntax:
fun <T> mutableSetOf( vararg elements: T): MutableSet<T>
Description:
- This function returns a set of given elements, which can be both read and written.
- The returned set preserves the element iteration order.
Kotlin program of mutableSetOf() function :
Kotlin
fun main(args: Array<String>){ //declaring a mutable set of integers val mutableSetA = mutableSetOf<Int>( 1 , 2 , 3 , 4 , 3); println(mutableSetA) //declaring a mutable set of strings val mutableSetB = mutableSetOf<String>("Geeks","for" , "geeks"); println(mutableSetB) //declaring an empty mutable set of integers val mutableSetC = mutableSetOf<Int>() println(mutableSetC)} |
Output:
[1, 2, 3, 4] [Geeks, for, geeks] []
Adding and removing elements in a set –
We can add elements in a mutable set using the add() function, and remove an elements using remove () function.
Example :
Kotlin
fun main(args: Array<String>){ //declaring a mutable set of integers val seta = mutableSetOf( 1 , 2 , 3 , 4 , 3); println(seta); //adding elements 6 & 7 seta.add(6); seta.add(7); println(seta); //removing 3 from the set seta.remove(3); println(seta); //another way to add elements is by using listOf() function seta += listOf(8,9) println(seta)} |
Output:
[1, 2, 3, 4] [1, 2, 3, 4, 6, 7] [1, 2, 4, 6, 7] [1, 2, 4, 6, 7, 8, 9]
Set Indexing –
Using index functions indexOf() , lastIndexOf() we can get the index of the specified element. And we can also find the elements at some specific index using elementAt() function.
Kotlin program of using index –
Kotlin
fun main(args: Array<String>) { val captains = mutableSetOf("Kohli","Smith","Root","Malinga","Rohit","Dhawan") println("The element at index 2 is: "+captains.elementAt(2)) println("The index of element is: "+captains.indexOf("Smith")) println("The last index of element is: "+captains.lastIndexOf("Rohit"))} |
Output:
The element at index 2 is: Root The index of element is: 1 The last index of element is: 4
Set first and last element –
We can get the first and element of a set using first() and last() functions.
Kotlin program –
Kotlin
fun main(args: Array<String>){ val captains = mutableSetOf(1,2,3,4,"Kohli","Smith", "Root","Malinga","Dhawan","Rohit") println("The first element of the set is: "+captains.first()) println("The last element of the set is: "+captains.last())} |
Output:
The first element of the set is: 1 The last element of the set is: Dhawan
Traversal in a mutableSet –
We can run a for loop with an iterator which traverse all the items in the set .
Kotlin
fun main(args: Array<String>){ //declaring a mutable set of integers val seta = mutableSetOf( 1 , 2 , 3 , 4 , 3); //traversal of seta using an iterator 'item' for(item in seta) println( item )} |
Output:
1 2 3 4
contains() and containsAll() functions –
Both the methods are used to check whether an element is present in the set or not?
Kotlin program of using contains() and containsAll() function –
Kotlin
fun main(args: Array<String>){ val captains = mutableSetOf(1,2,3,4,"Kohli","Smith", "Root","Malinga","Rohit","Dhawan") var name = "Dhawan" println("The set contains the element $name or not?" + " "+captains.contains(name)) var num = 5 println("The set contains the element $num or not?" + " "+captains.contains(num)) println("The set contains the given elements or not?" + " "+captains.containsAll(setOf(1,3,"Root")))} |
Output:
The set contains the element Dhawan or not? true The set contains the element 5 or not? false The set contains the given elements or not? true
Checking equality of empty sets and use of isEmpty() functions –
fun <T> mutableSetOf(): mutableSet<T>
This syntax returns an empty set of specific type.
Kotlin program of using isEmpty() function –
Kotlin
fun main(args: Array<String>) { //creating an empty set of strings val seta = mutableSetOf<String>() //creating an empty set of integers val setb = mutableSetOf<Int>() //checking if set is empty or not println("seta.isEmpty() is ${seta.isEmpty()}") // Since Empty sets are equal //checking if two sets are equal or not println("seta == setb is ${seta == setb}") println(seta) //printing first set} |
Output :
seta.isEmpty() is true seta == setb is true []
