Scala Collections - Queue

Queue is First In First Out, FIFO data structure and allows to insert and retrieve elements in FIFO manner.

Declaring Queue Variables

The following is the syntax for declaring an Queue variable.

Syntax

val queue = Queue(1, 2, 3, 4, 5)

Here, queue is declared as an Queue of numbers. Value can be added at front by using commands like the following −

Command

queue.enqueue(6)

Value can be retrived at front by using commands like the following −

Command

queue.dequeue()

Processing Queue

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

Example

import scala.collection.mutable.Queue
object Demo {
   def main(args: Array[String]) = {
      var queue = Queue(1, 2, 3, 4, 5);
      // Print queue elements
      queue.foreach{(element:Int) => print(element + " ")}
      println();
      // Print first element
      println("First Element: " + queue.front)
      // Add an element
      queue.enqueue(6);
      // Print queue elements
      queue.foreach{(element:Int) => print(element+ " ")}
      println();
      // Remove an element
      var dq = queue.dequeue;
      // Print dequeued element
      println("Dequeued Element: " + dq)
      // Print queue elements
      queue.foreach{(element:Int) => print(element+ " ")}
   }
}

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

1 2 3 4 5
First Element: 1
1 2 3 4 5 6
Dequeued Element: 1
2 3 4 5 6