This topic is about 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
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