Open In App

Scala Lists

Last Updated : 14 Mar, 2019
Comments
Improve
Suggest changes
7 Likes
Like
Report
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. Following are the point of difference between lists and array in Scala:
  • Lists are immutable whereas arrays are mutable in Scala.
  • Lists represents a linked list whereas arrays are flat.
Syntax: 
 val variable_name: List[type] = List(item1, item2, item3) or val variable_name = List(item1, item2, item3)
Some important points about list in Scala:
  • In a Scala list, each element must be of the same type.
  • The implementation of lists uses mutable state internally during construction.
  • In Scala, list is defined under scala.collection.immutable package.
  • A List has various methods to add, prepend, max, min, etc. to enhance the usage of list.
Example: Scala 
// Scala program to print immutable lists import scala.collection.immutable._ // Creating object object GFG {  // Main method  def main(args:Array[String])  {   // Creating and initializing immutable lists  val mylist1: List[String] = List("Geeks", "GFG",  "GeeksforGeeks", "Geek123")  val mylist2 = List("C", "C#", "Java", "Scala",  "PHP", "Ruby")  // Display the value of mylist1  println("List 1:")  println(mylist1)  // Display the value of mylist2 using for loop  println("\nList 2:")  for(mylist<-mylist2)  {  println(mylist)  }  } }
Output: 
 List 1: List(Geeks, GFG, GeeksforGeeks, Geek123) List 2: C C# Java Scala PHP Ruby
In above example simply we are printing two lists. Example: Scala 
// Scala program to illustrate the // use of empty list import scala.collection.immutable._ // Creating object object GFG {  // Main method  def main(args:Array[String])  {  // Creating an Empty List.  val emptylist: List[Nothing] = List()  println("The empty list is:")  println(emptylist)  } }
Output: 
 The empty list is: List()
Above example shows that the list is empty or not. Example: Scala 
// Scala program to illustrate the  // use of two dimensional list import scala.collection.immutable._ // Creating object object GFG {  // Main method  def main(args:Array[String])  {  // Creating a two-dimensional List.  val twodlist: List[List[Int]] =  List(  List(1, 0, 0),  List(0, 1, 0),  List(0, 0, 1)  )  println("The two dimensional list is:")  println(twodlist)  } }
Output: 
 The two dimensional list is: List(List(1, 0, 0), List(0, 1, 0), List(0, 0, 1))
Basic Operations on Lists
The following are the three basic operations which can be performed on list in scala:
  1. head: The first element of a list returned by head method. Syntax: 
     list.head //returns head of the list
    Example: Scala 
    // Scala program of a list to  // perform head operation import scala.collection.immutable._ // Creating object object GFG {  // Main method  def main(args:Array[String])  {  // Creating a List.  val mylist = List("C", "C#", "Java", "Scala",  "PHP", "Ruby")  println("The head of the list is:")  println(mylist.head)  } }
    Output: 
     The head of the list is: C
  2. tail: This method returns a list consisting of all elements except the first. Syntax: 
     list.tail //returns a list consisting of all elements except the first
    Example: Scala 
    // Scala program to perform // tail operation of a list import scala.collection.immutable._ // Creating object object GFG {  // Main method  def main(args:Array[String])  {  // Creating a List.  val mylist = List("C", "C#", "Java", "Scala",  "PHP", "Ruby")  println("The tail of the list is:")  println(mylist.tail)  } }
    Output: 
     The tail of the list is: List(C#, Java, Scala, PHP, Ruby)
  3. isEmpty: This method returns true if the list is empty otherwise false. Syntax: 
     list.isEmpty //returns true if the list is empty otherwise false.
    Example: Scala 
    // Scala program to perform // isEmpty operation of a list import scala.collection.immutable._ // Creating object object GFG {  // Main method  def main(args:Array[String])  {    // Creating a List.  val mylist = List("C", "C#", "Java", "Scala",  "PHP", "Ruby")  println("List is empty or not:")  println(mylist.isEmpty)  } }
    Output: 
     List is empty or not: false
How to create a uniform list in Scala
Uniform List can be created in Scala using List.fill() method. List.fill() method creates a list and fills it with zero or more copies of an element. Syntax: 
 List.fill() //used to create uniform list in Scala
Example: Scala 
// Scala program to creating a uniform list  import scala.collection.immutable._ // Creating object object GFG {  // Main method  def main(args:Array[String])  {  // Repeats Scala three times.  val programminglanguage = List.fill(3)("Scala")   println( "Programming Language : " + programminglanguage )  // Repeats 2, 10 times.  val number= List.fill(8)(4)   println("number : " + number)  } }
Output: 
 Programming Language : List(Scala, Scala, Scala) number : List(4, 4, 4, 4, 4, 4, 4, 4)
Reversing List Order in Scala
The list order can be reversed in Scala using List.reverse method. List.reverse method can be used to reverse all elements of the list. Syntax: 
 list.reverse //used to reverse list in Scala
Example: Scala 
// Scala program of reversing a list order import scala.collection.immutable._ // Creating object object GFG {  // Main method  def main(args:Array[String])  {  val mylist = List(1, 2, 3, 4, 5)   println("Original list:" + mylist)    // reversing a list  println("Reverse list:" + mylist.reverse)  } }
Output: 
 Original list:List(1, 2, 3, 4, 5) Reverse list:List(5, 4, 3, 2, 1)

C

chaitanyashah707
Improve
Article Tags :

Explore

Lightbox