A mutable set is an extension of a set that supports adding and removing elements. Like a set, a mutable set does not provide its own function, but it does extend two interfaces: set and mutableCollection. Mutable sets also override all functions from their parent interfaces. This means that we can use all functions, including size, isEmpty, add, contains, and retainAll:

fun mutableSetFunction() {
 
     val mutableSetItems : MutableSet<Int>    = mutableSetOf(1,1,2,3,3,4,5,5)
     var mutableSetIterator =  mutableSetItems.iterator()
 
     while (mutableSetIterator.hasNext()) {
         print(mutableSetIterator.next())
     }
 
     println("")
     println("Set size ${mutableSetItems.size}")
 
     var item = 5
     var result = mutableSetItems.contains(item)
     println("Mutable item contains $item = $result")
 
     result = mutableSetItems.remove(item)
     println("Mutable item removed $item = $result")
 
     item = 6
     println("$item is added")
     mutableSetItems.add(item)
     println(mutableSetItems)
 
     // Keep only mentioned items in list
     mutableSetItems.retainAll(listOf(2,4,6,8))
 
     // Clear all items
     mutableSetItems.clear()
 
     var miniCollection = listOf(1,1,2,3,3)
     if (mutableSetItems.size == 0 ) {
         println("List is clear, add mini collection")
         mutableSetItems.addAll(miniCollection)
         println(mutableSetItems)
     }
 }

Implement this example and check each function of the mutable set one by one.