### Kotlin mutableSetOf

In this guide, we will learn about the Kotlin mutableSetOf() function with lots of examples.

# What is mutableSetOf()?

mutableSetOf() is a function in Kotlin's standard library that creates an instance of a mutable set. A set is a collection that doesn't allow duplicate elements. When we say "mutable," it means that the set can be changed after it's been created. You can add, remove, or modify elements in a mutable set.

## Basic Syntax:

``val mutableSet: MutableSet<Type> = mutableSetOf(element1, element2, ...)``

# Examples with Outputs

Constructing a Mutable Set

``````val animals = mutableSetOf("Cat", "Dog", "Bird")
println(animals)  // Output: [Cat, Dog, Bird]``````

## Adding Elements to a Mutable Set

``````val veggies = mutableSetOf("Broccoli", "Carrot")
println(veggies)  // Output: [Broccoli, Carrot, Pepper]``````

## Removing Elements from a Mutable Set

``````val fruits = mutableSetOf("Apple", "Banana", "Cherry")
fruits.remove("Banana")
println(fruits)  // Output: [Apple, Cherry]``````

## Element Uniqueness in Mutable

Sets Remember, sets inherently ensure element uniqueness:

``````val numbers = mutableSetOf(1, 2, 2, 3)
println(numbers)  // Output: [1, 2, 3]``````

## Combining Two Mutable

Sets Merging retains unique elements:

``````val setA = mutableSetOf(1, 2, 3)
val setB = mutableSetOf(3, 4, 5)
println(setA)  // Output: [1, 2, 3, 4, 5]``````

## Checking for Elements

Using Kotlin's in operator:

``````val colors = mutableSetOf("Red", "Green", "Blue")
println("Yellow" in colors)  // Output: false``````

## Clearing All Elements

``````val letters = mutableSetOf('a', 'b', 'c')
letters.clear()
println(letters)  // Output: []``````

## Retaining Specific Elements

Retain elements that are present in another collection:

``````val setOne = mutableSetOf(1, 2, 3, 4)
setOne.retainAll(listOf(3, 4, 5, 6))
println(setOne)  // Output: [3, 4]
``````

# Conclusion

In this guide, we learned everything about Kotlin mutableSetOf() with lots of examples. So mutableSetOf() is a function in Kotlin's standard library, tailored to instantiate a mutable set. Unlike its immutable counterpart created by setOf(), a mutable set allows additions, modifications, and removal of elements post-creation.