C# | Queue<T>.TrimExcess Method with Examples

Last Updated : 01 Feb, 2019

Queue represents a first-in, first out collection of object. It is used when you need a first-in, first-out access to items. When you add an item in the list, it is called enqueue, and when you remove an item, it is called Dequeue. Queue<T>.TrimExcess Method is used to set the capacity to the actual number of elements in the Queue<T>, if that number is less than 90 percent of current capacity. A queue is an unbounded data structure and there is no method available to calculate the capacity of Queue in C#. It is dynamic and depends on the system memory. This method is generally used in memory management of the large queue. Queue Properties:

Enqueue adds an element to the end of the Queue.
Dequeue removes the oldest element from the start of the Queue.
Peek returns the oldest element that is at the start of the Queue but does not remove it from the Queue.
The capacity of a Queue is the number of elements the Queue can hold.
As elements are added to a Queue, the capacity is automatically increased as required by reallocating the internal array.
Queue accepts null as a valid value for reference types and allows duplicate elements.

Syntax:

public void TrimExcess ();

Note:

This method can be used to minimize a collection's memory overhead if no new elements will be added to the collection.
To reset a Queue<T> to its initial state, call the Clear method before calling the TrimExcess method.
Trimming an empty Queue<T> sets the capacity of the Queue<T> to the default capacity.

Below given is an example to understand the implementation in a better way: Example:

CSHARP

// C# code to set the capacity to the
// actual number of elements in the Queue
using System;
using System.Collections.Generic;

class GFG {
    
    // Driver code
    public static void Main()
    {
        
        // Creating a Queue of strings
        Queue<string> myQueue = new Queue<string>();

        // Inserting elements into Queue
        myQueue.Enqueue("1st");
        myQueue.Enqueue("2nd");
        myQueue.Enqueue("3rd");
        myQueue.Enqueue("4th");
        myQueue.Enqueue("5th");

        // To display number of elements in Queue
        Console.WriteLine(myQueue.Count);
        
        // Removing all the elements from Queue
        myQueue.Clear();

        // using TrimExcess method
        myQueue.TrimExcess();

        // To display number of elements in Queue
        Console.WriteLine(myQueue.Count);
    }
}