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 that returns a mutable hashSet, which can be both read and written. The HashSet class store all the elements using the hashing mechanism.

Syntax:

fun <T> hashSetOf(vararg elements: T): HashSet<T>

It returns a new HashSet with the given elements but does not guarantee the order sequence specified at the storing time.

Example of hashSetOf()  

Output: 

[1, 2, 3]
[Geeks, for, geeks] 

Adding and removing elements in hashset –

• 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:

Output: 

[]
[1, 2, 4, 5, 6]
[1, 4, 5, 6] 

Traversal in hashSet-

We can traverse a hashSet using an iterator in a loop.

Output: 

1
2
3
5

HashSet 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 –  

Output: 

The element at index 2 is: Malinga
The index of element is: 4
The last index of element is: 0 

contains() and containsAll() functions –

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 – 

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 

Checking equality of empty hash sets and use of isEmpty() functions –

fun <T> hashSetOf(): hashSet<T>

This syntax returns an empty hash set of a specific type.
Kotlin program of using isEmpty() function – 

Output : 

seta.isEmpty() is true
seta == setb is true

 hashSetOf() is a function in Kotlin that creates a new hash set. A hash set is an unordered collection of unique elements that provides constant time performance for adding, removing, and checking the presence of an element.

Here’s an example of using hashSetOf() to create a set of integers:

Output:

Numbers: [1, 3, 4]
Contains 5: false
 

In this example, we create a new hash set of integers using the hashSetOf() function and add three elements to it: 1, 2, and 3. We then add the element 4 to the set and remove 2 from the set. Finally, we check if the set contains the element 5 using the contains() function and print the result to the console.

Advantages of hashSetOf():

1. The hash set data structure provides O(1) time complexity for adding, removing, and checking the presence of an element, making it very efficient for handling large sets of data.
2. The hash set ensures that the elements are unique, so it is a good choice for keeping track of a collection of distinct values.
3. The hashSetOf() function is easy to use and provides a simple way to create a new hash set with initial elements.

Disadvantages of hashSetOf():

1. The order of elements in a hash set is not guaranteed, so the iteration order may not be the same as the insertion order.
2. The performance of the hash set can degrade if the hash function produces many collisions, which can cause the set to become slower than other data structures such as an array or a linked list.