Working on Queue Using C#

Introduction

A Queue represents a first-in, first-out collection of objects. An example of a queue is a line of people waiting. Queue<T> is the class in the System.Collection.Generic Namespace, where T specifies the type of elements in the queue. In this article I explain the constructor, properties and methods of the Queue class.

Constructors

1. Queue<T> Constructor - Initializes a new instance of the Queue<T> class that is empty. The next lines shows how we create the empty queue.
   
   Queue<string> queue = new Queue<string>();
    
2. Queue<T> Constructor (IEnumerable<T>) - Initializes a new instance of the Queue<T> class that contains elements copied from the specified collection.
   
   string[] courses = { "MCA","MBA", "BCA","BBA", "BTech","MTech" };
   Queue<string> queue = new Queue<string>(courses);
    
3. Queue<T> Constructor (Int32) - Initializes a new instance of the Queue<T> class that is empty and has the specified initial capacity.
   
   Queue<string> queue = new Queue<string>(4);

Properties

Count - Gets the number of elements contained in the Queue<T>. For example:

namespace Queue

{

    class Program

    {

        static void Main(string[] args)

        {

            string[] courses = { "MCA", "MBA", "BCA", "BBA", "BTech", "MTech" };

            Queue<string> queue1 = new Queue<string>();

            Queue<string> queue2 = new Queue<string>(courses);

            Queue<string> queue3 = new Queue<string>(4);

            Console.WriteLine("Number of elements in queue1:" + queue1.Count());

            Console.WriteLine("Number of elements in queue2:" + queue2.Count());

            Console.WriteLine("Number of elements in queue3:" + queue3.Count());

        }

    }

}

OUTPUT

Methods

1. Enqueue - Adds an object to the end of the Queue<T>. For example:
    

   namespace Queue

   {

      class Program

       {

          static void Main(string[] args)

           {

              Queue<string> queue1 = new Queue<string>();

               queue1.Enqueue("MCA");

               queue1.Enqueue("MBA");

               queue1.Enqueue("BCA");

               queue1.Enqueue("BBA");

              Console.WriteLine("The elements in the queue are:");

              foreach (string s in queue1)

               {

                  Console.WriteLine(s);

               }

           }

       }

   }
   
   OUTPUT
   
   

   
    

2. Dequeue - Removes and returns the object at the beginning of the Queue<T>. For example:
   
   namespace Queue

   {

      class Program

       {

          static void Main(string[] args)

           {

              Queue<string> queue1 = new Queue<string>();

               queue1.Enqueue("MCA");

               queue1.Enqueue("MBA");

               queue1.Enqueue("BCA");

               queue1.Enqueue("BBA");

              Console.WriteLine("The elements in the queue are:");

              foreach (string s in queue1)

               {

                  Console.WriteLine(s);

               }

               queue1.Dequeue();//Removes the first element that enter in the queue here the first element is MCA

               queue1.Dequeue();//Removes MBA

              Console.WriteLine("After removal the elements in the queue are:");

              foreach (string s in queue1)

               {

                  Console.WriteLine(s);

               }

           }

       }

   }
   
   OUTPUT
   
   

   
   

    

3. Contain - Determines whether an element is in the Queue<T>. For example:
    

   namespace Queue

   {

      class Program

       {

          static void Main(string[] args)

           {

              Queue<string> queue1 = new Queue<string>();

               queue1.Enqueue("MCA");

               queue1.Enqueue("MBA");

               queue1.Enqueue("BCA");

               queue1.Enqueue("BBA");

              Console.WriteLine("The elements in the queue are:");

              foreach (string s in queue1)

               {

                  Console.WriteLine(s);

               }

              Console.WriteLine("The element MCA is contain in the queue:" + queue1.Contains("MCA"));

              Console.WriteLine("The element BCA is contain in the queue:" + queue1.Contains("BCA"));

              Console.WriteLine("The element MTech is contain in the queue:" + queue1.Contains("MTech"));

           }

       }

   }
   
   OUTPUT
   
   

   
    

4. Clear - Removes all objects from theQueue<T>. For example:
   
   

   namespace Queue

   {

      class Program

       {

          static void Main(string[] args)

           {

              Queue<string> queue1 = new Queue<string>();

               queue1.Enqueue("MCA");

               queue1.Enqueue("MBA");

               queue1.Enqueue("BCA");

               queue1.Enqueue("BBA");

              Console.WriteLine("The elements in the queue are:"+queue1.Count());

               queue1.Clear();

              Console.WriteLine("The elements in the queue are after the clear method:" + queue1.Count());           

           }

       }

   }
   
   OUTPUT
   
   

   
   
   
5. Peek - Returns the object at the beginning of the Queue<T> without removing it. For example:
    

   namespace Queue

   {

      class Program

       {

          static void Main(string[] args)

           {

              Queue<string> queue1 = new Queue<string>();

               queue1.Enqueue("MCA");

               queue1.Enqueue("MBA");

               queue1.Enqueue("BCA");

               queue1.Enqueue("BBA");

              Console.WriteLine("Peek the first item from the queue is:" + queue1.Peek());

               queue1.Dequeue();

              Console.WriteLine("Peek the next item from the queue is:" + queue1.Peek());        

           }

       }

   }
   
   OUTPUT
   
   
    

6. ToArray - Copies the Queue<T> elements to a new array. For example:
   
   

   namespace Queue

   {

      class Program

       {

          static void Main(string[] args)

           {

              Queue<string> queue1 = new Queue<string>();

               queue1.Enqueue("MCA");

               queue1.Enqueue("MBA");

               queue1.Enqueue("BCA");

               queue1.Enqueue("BBA");

              Console.WriteLine("The queue elements are:");

              foreach (string s in queue1)

               {

                  Console.WriteLine(s);

               }

              Queue<string> queue2 = new Queue<string>(queue1.ToArray());

              Console.WriteLine("\nContents of the copy");

              foreach (string n in queue2)

               {

                  Console.WriteLine(n);

               }

           }

       }

   }

7. OUTPUT

8. 
   
   Summary
   

   In this article I explained the Queue<> class and the various methods and properties of it.