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
- 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>();
- 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);
- 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
![pic1.jpg]()
Methods
- 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
![pic2.jpg]()
- 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
![pic3.jpg]()
- 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
![pic4.jpg]()
- 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
![pic5.jpg]()
- 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
![pic6.jpg]()
- 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);
}
}
}
}
-
OUTPUT
-
![pic7.jpg]()
Summary
In this article I explained the Queue<> class and the various methods and properties of it.