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How to merge lists in Scala

  • Last Updated : 13 Jul, 2021

A list is a collection which contains immutable data. List represents linked list in Scala. The Scala List class holds a sequenced, linear list of items. Lists are immutable and represents a linked list.
Syntax of List: 
 

val variable_name: List[type] = List(item1, item2, item3)
or
val variable_name = List(item1, item2, item3)

Below are three different way to merge lists: 
 

  • using the ++
  • Using :::
  • Using concat

Following are the various ways to merge two lists in Scala:
 

By using ++ method

Example: 
 

Scala




// Scala program to merge lists
 
// Creating object
object GFG
{
    // Main method
    def main(args:Array[String])
    {
        // Creating Lists
        val a = List("geeks", "for", "geeks")
        val b = List("is", "a", "computer science", "portal")
        val c = List("for", "geeks")
         
        // Merging Lists
        val d = a ++ b ++ c
        println("After merging lists ")
        println(d)
    }
}    
    
Output: 



After merging lists 
List(geeks, for, geeks, is, a, computer science, portal, for, geeks)

 

In above example we are using ++ method to concatenate lists. This method is used consistently across immutable collections  
 

By using :::

If we using the List class frequently, we may prefer using ::: method.
Example: 
 

Scala




// Scala program to merging two lists
 
// Creating object
object GFG
{
    // Main method
    def main(args:Array[String])
    {
        // Creating a List.
        val a = List("Languages", "are")
        val b = List("C++", "Java", "C#", "Python", "Scala")
         
        // Merging two lists
        val c = a ::: b
         
        println("After merging lists")
        println(c)
    }
}    
    

  
 

By using concat method

Example:
 

Scala




// Scala program merging two lists
 
// Creating object
object GFG
{
    // Main method
    def main(args:Array[String])
    {
        // Creating a List.
        val a = List(1, 2, 3)
        val b = List(4, 5, 6)
         
        // concatenate two lists
        val c = List.concat(a, b)
        println("After merging lists")
        println(c)
    }
}    
Output: 
After merging lists
List(1, 2, 3, 4, 5, 6)

 




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