Scala Set is a collection of pairwise different elements of the same type. In other words, a Set is a collection that contains no duplicate elements. HashSet implements immutable sets and uses hash table. Elements insertion order is not preserved.

Declaring HashSet Variables

The following is the syntax for declaring an HashSet variable.

Syntax

var z : HashSet[String] = HashSet("Zara","Nuha","Ayan")

Here, z is declared as an hash-set of Strings which has three members. Values can be added by using commands like the following −

Command

var myList1: HashSet[String] = myList + "Naira";

Processing HashSet

Below is an example program of showing how to create, initialize and process HashSet −

Example

import scala.collection.immutable.HashSet
object Demo {
   def main(args: Array[String]) = {
      var mySet: HashSet[String] = HashSet("Zara","Nuha","Ayan");
      // Add an element
      var mySet1: HashSet[String] = mySet + "Naira";
      // Remove an element
      var mySet2: HashSet[String] = mySet - "Nuha";
      // Create empty set
      var mySet3: HashSet[String] = HashSet.empty[String];
      println(mySet);
      println(mySet1);
      println(mySet2);
      println(mySet3);	  
   }
}

Save the above program in Demo.scala. The following commands are used to compile and execute this program.

Command

>scalac Demo.scala
>scala Demo

Output

HashSet(Zara, Nuha, Ayan)
HashSet(Zara, Nuha, Ayan, Naira)
HashSet(Zara, Ayan)
HashSet()