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HashMap in Scala

By IncludeHelp Last updated : November 14, 2024

Scala HashMap

HashMap is a collection based on maps and hashes. It stores key-value pairs.

Denoted by

HashMap<Key, Value> or HashMap<K, V>

Syntax

var hashmap = HashMap("key1" -> "value1", ...);

Import HashMap

To import HashMap to our Scala program, the following statement is used,

scala.collection.mutable.HashMap

Now, let's see the operations on HashMap in Scala,

Example 1: Creating HashMap in Scala

Creating a HashMap in Scala is an easy process. A HashMap in Scala can be empty also.

import scala.collection.mutable.HashMap 

object MyClass {
    def main(args: Array[String]): Unit = {
        var hashmap = new HashMap()
        var hashmap2 = HashMap(1 -> "K1200" , 2 -> "Thunderbird 350", 3 -> "CBR 1000")
        println("Empty HashMap : "+hashmap)
        println("Hashmap with elements : "+hashmap2)
    }
}

Output

Empty HashMap : HashMap()
Hashmap with elements : HashMap(1 -> K1200, 2 -> Thunderbird 350, 3 -> CBR 1000)

Example 2: Accessing elements of HashMap

The elements of a HashMap can be accessed in Scala using foreach loop as shown below,

import scala.collection.mutable.HashMap 

object MyClass {
    def main(args: Array[String]): Unit = {
        var hashmap = HashMap(1 -> "K1200" , 2 -> "Thunderbird 350", 3 -> "CBR 1000")
        hashmap.foreach  
        {   
            case (key, value) => println (key + " -> " + value)          
        }   
    }
}

Output

1 -> K1200
2 -> Thunderbird 350
3 -> CBR 1000

Example 3: Adding elements to the HashMap

Adding of elements to the HashMap can also be done in Scala programming language. The + operator is used to add new key-value pair to the HashMap.

import scala.collection.mutable.HashMap 

object MyClass {
    def main(args: Array[String]): Unit = {
        var hashmap = HashMap(1 -> "K1200" , 2 -> "Thunderbird 350", 3 -> "CBR 1000")
        println("The HashMap is : "+hashmap)
        println("Adding new elements to the HashMap. ")
        hashmap += (7 -> "HD Fat Boy")
        println("The HashMap is : "+hashmap)
    }
}

Output

The HashMap is : HashMap(1 -> K1200, 2 -> Thunderbird 350, 3 -> CBR 1000)
Adding new elements to the HashMap. 
The HashMap is : HashMap(1 -> K1200, 2 -> Thunderbird 350, 3 -> CBR 1000, 7 -> HD Fat Boy)

Example 4: Removing element from HashMap in Scala

In Scala removing elements from a HashMap is also possible. The - operator is used to remove elements from HashMap.

import scala.collection.mutable.HashMap 

object MyClass {
    def main(args: Array[String]): Unit = {
        var hashmap = HashMap(1 -> "K1200" , 2 -> "Thunderbird 350", 3 -> "CBR 1000")
        println("The HashMap is : "+hashmap)
        println("removing elements to the HashMap. ")
        hashmap -= 3
        println("The HashMap is : "+hashmap)
    }
}

Output

The HashMap is : HashMap(1 -> K1200, 2 -> Thunderbird 350, 3 -> CBR 1000)
removing elements to the HashMap. 
The HashMap is : HashMap(1 -> K1200, 2 -> Thunderbird 350)