Scala Collections - Vector

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Scala Vector is a general purpose immutable data structure where elements can be accessed randomly. It is generally used for large collections of data.

Declaring Vector Variables

The following is the syntax for declaring an Vector variable.

Syntax

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

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

Command

var vector1: Vector[String] = z + "Naira";

Processing Vector

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

Example

import scala.collection.immutable.Vector
object Demo {
   def main(args: Array[String]) = {
      var vector: Vector[String] = Vector("Zara","Nuha","Ayan");
      // Add an element
      var vector1: Vector[String] = vector :+ "Naira";
      // Reverse an element
      var vector2: Vector[String] = vector.reverse;
      // sort a vector
      var vector3: Vector[String] = vector1.sorted;
      println(vector);
      println(vector1);
      println(vector2);
      println(vector3);	  
   }
}

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

Vector(Zara, Nuha, Ayan)
Vector(Zara, Nuha, Ayan, Naira)
Vector(Ayan, Nuha, Zara)
Vector(Ayan, Naira, Nuha, Zara)

Accessing Elements

You can access elements in a Vector using their indices. It is a constant-time operation. So, Vectors are efficient for random access.

Example

object Demo {
   def main(args: Array[String]) = {
      var vector: Vector[String] = Vector("Zara", "Nuha", "Ayan")
      println("First element: " + vector(0))
      println("Second element: " + vector(1))
      println("Third element: " + vector(2))
   }
}

Save the above program in Demo.scala. Use the following commands to compile and execute this program.

Command

> scalac Demo.scala
> scala Demo

Output

First element: Zara
Second element: Nuha
Third element: Ayan

Updating Elements

Since vectors are immutable. So, if you update an element, it creates a new Vector with the updated value. Try following example for updating elements -

Example

object Demo {
   def main(args: Array[String]) = {
      var vector: Vector[String] = Vector("Zara", "Nuha", "Ayan")
      var updatedVector: Vector[String] = vector.updated(1, "Naira")

      println("Original vector: " + vector)
      println("Updated vector: " + updatedVector)
   }
}

Save the above program in Demo.scala. Use the following commands to compile and execute this program.

Command

> scalac Demo.scala
> scala Demo

Output

Original vector: Vector(Zara, Nuha, Ayan)
Updated vector: Vector(Zara, Naira, Ayan)

Concatenating Vectors

You can concatenate two or more Vectors using the ++ operator. You can also use the Vector.++() method for concatenating vectors. Try following example for concatenating vectors -

Example

object Demo {
   def main(args: Array[String]) = {
      var vector1: Vector[String] = Vector("Zara", "Nuha")
      var vector2: Vector[String] = Vector("Ayan", "Naira")

      // Use ++ operator
      var concatenatedVector = vector1 ++ vector2
      println("vector1 ++ vector2: " + concatenatedVector)

      // Use ++ method
      concatenatedVector = vector1.++(vector2)
      println("vector1.++(vector2): " + concatenatedVector)
   }
}

Save the above program in Demo.scala. Use the following commands to compile and execute this program.

Command

> scalac Demo.scala
> scala Demo

Output

vector1 ++ vector2: Vector(Zara, Nuha, Ayan, Naira)
vector1.++(vector2): Vector(Zara, Nuha, Ayan, Naira)

Iterating over Vectors

You can iterate over elements in a Vector using a foreach loop or other iteration methods.

Example

Try following example for iterating over a vector -

object Demo {
   def main(args: Array[String]) = {
      var vector: Vector[String] = Vector("Zara", "Nuha", "Ayan")

      vector.foreach { element =>
         println(element)
      }
   }
}

Save the above program in Demo.scala. Use the following commands to compile and execute this program.

Command

> scalac Demo.scala
> scala Demo

Output

Zara
Nuha
Ayan

Using map() Method

You can transform a Vector using map() function to each element. This is used for performing operations on each element and creating a new Vector with the transformed elements.

Example

Try following example for using map() method -

object Demo {
   def main(args: Array[String]) = {
      var vector: Vector[Int] = Vector(1, 2, 3)

      var doubledVector: Vector[Int] = vector.map(_ * 2)
      println("Doubled vector: " + doubledVector)
   }
}

Save the above program in Demo.scala. Use the following commands to compile and execute this program.

Command

> scalac Demo.scala
> scala Demo

Output

Doubled vector: Vector(2, 4, 6)

Using filter() Method

You can filter elements using the filter() method in a Vector based on a predicate function. It creates a new Vector containing only the elements that satisfy the given predicate.

Example

Try following example for using filter() method -

object Demo {
   def main(args: Array[String]) = {
      var vector: Vector[Int] = Vector(1, 2, 3, 4, 5)

      var evenVector: Vector[Int] = vector.filter(_ % 2 == 0)
      println("Even vector: " + evenVector)
   }
}

Save the above program in Demo.scala. Use the following commands to compile and execute this program.

Command

> scalac Demo.scala
> scala Demo

Output

Even vector: Vector(2, 4)

Scala Vector Summary

• Vectors are immutable data structures. These are optimized for random access and large collections. Vectors are also efficient for updates and appends.
• You can create vectors using the Vector companion object and add elements using the :+
• You can perform various operations on vectors, like reversing, sorting, and mapping.
• You can also perform operations, like concatenation, finding the length, retrieving elements at specific positions, and checking if the vector contains certain elements.
• There are various vector methods, like, head, tail, isEmpty, foreach, map, flatMap, filter, and fold.