Kotlin hashSetOf() - GeeksforGeeks

18 Aug, 2021
Kotlin HashSet is a generic unordered collection of elements and it does not contain duplicate elements. It implements the set interface. hashSetOf() is a function which returns a mutable hashSet, which can be both read and written. The HashSet class store all the elements using hashing mechanism.
Syntax: 
fun <T> hashSetOf(vararg elements: T): HashSet<T>
It returns a new HashSet with the given elements but does not guarantee about the order sequence specified at the storing time.
Example of hashSetOf()  
Kotlin
fun main(args: Array<String>){      //declaring a hash set of integers    val seta = hashSetOf(1,2,3,3);    //printing first set    println(seta)          //declaring a hash set of strings    val setb = hashSetOf("Geeks","for","geeks");    println(setb);      }
Output: 
[1, 2, 3]
[Geeks, for, geeks] 
We can add elements in a hashset using add() and addAll() functions.
We can remove an element using remove() function.
Kotlin program of using the add() and remove() method –  
Kotlin
fun main(args: Array<String>){    //declaring a hash set of integers    val seta = hashSetOf<Int>();    println(seta)      //adding elements    seta.add(1)    seta.add(2)      //making an extra set to add it in seta    val newset = setOf(4,5,6)    seta.addAll(newset)      println(seta)      //removing 2 from the set    seta.remove(2)    println(seta)    }
Output: 
[]
[1, 2, 4, 5, 6]
[1, 4, 5, 6] 
We can traverse a hashSet using an iterator in a loop.
Kotlin
fun main(args: Array<String>){    //declaring a hash set of integers    val seta = hashSetOf(1,2,3,5);          //traversing in a set using a for loop    for(item in seta)        println(item)}
Output: 
1
2
3
5
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 = hashSetOf("Kohli","Smith","Root","Malinga","Rohit","Dhawan")     println("The element at index 2 is: "+captains.elementAt(3))     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: Malinga
The index of element is: 4
The last index of element is: 0 
Both the methods are used to check whether an element is present in the Hashset or not? Kotlin program of using contains() and containsAll() function – 
Kotlin
fun main(args: Array<String>){    val captains = hashSetOf(1,2,3,4,"Kohli","Smith",        "Root","Malinga","Rohit","Dhawan")      var name = "Rohit"    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,"Dhawan","Warner")))}
Output: 
The set contains the element Rohit or not?   true
The set contains the element 5 or not?   false
The set contains the given elements or not?   false 
fun <T> hashSetOf(): hashSet<T>
This syntax returns an empty hash set of a specific type.Kotlin program of using isEmpty() function – 
Kotlin
fun main(args: Array<String>) {    //creating an empty hash set of strings    val seta = hashSetOf<String>()    //creating an empty hashset of integers    val setb =hashSetOf<Int>()      //checking if set is empty or not    println("seta.isEmpty() is ${seta.isEmpty()}")     // Since Empty hashsets are equal     //checking if two hash sets are equal or not    println("seta == setb is ${seta == setb}")}
Output : 
seta.isEmpty() is true
seta == setb is true
 
singghakshay
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