fixed and dynamic data structures

This example contrasts the use of a fixed data structure (an array) with a dynamic data structure (a List(Of T)).

Once it has been initialized an array is fixed in size whereas a List(Of T) increases its capacity automatically as new items are added.

It is still possible to increase an array's size using the Array.Resize method but what this does internally is to create a new array of the required size and then copy the previous array's elements to the new array.

Internally, a List

Imports System

Imports System.Collections.Generic

Module Test

   Sub Main()

      Dim a() As String = {"A", "B", "C", "D"}

      Array.Resize(a, 6)

      a(4) = "E"

      a(5) = "F"

      Console.Write("The elements of the array are : ")

      For Each s As String in a

        Console.Write("{0} ", s)

      Next

 

      Console.WriteLine()

      ' now do same thing using a List(Of String)

      Dim l As New List(Of String) From {"A", "B", "C", "D"}

      Console.WriteLine("The initial capacity of the list is {0}", l.Capacity)

      l.Add("E")

      l.Add("F")

      Console.Write("The elements of the list are : ")

      For Each s As String in a

        Console.Write("{0} ", s)

      Next
     

      Console.WriteLine()

      Console.WriteLine("The capacity of the list has now been doubled to {0}", l.Capacity)

      Console.ReadKey()

   End Sub

End Module