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

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);
    }
}

Reference:

• https://docs.microsoft.com/en-us/dotnet/api/system.collections.generic.queue-1.trimexcess?view=netframework-4.7.2