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ArrayList.TrimToSize Method

Sets the capacity to the actual number of elements in the ArrayList.

Namespace: System.Collections
Assembly: mscorlib (in mscorlib.dll)

'Declaration
Public Overridable Sub TrimToSize
'Usage
Dim instance As ArrayList

instance.TrimToSize
public void TrimToSize ()
public function TrimToSize ()
Not applicable.

Exception typeCondition

NotSupportedException

The ArrayList is read-only.

-or-

The ArrayList has a fixed size.

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 ArrayList to its initial state, call the Clear method before calling TrimToSize. Trimming an empty ArrayList sets the capacity of the ArrayList to the default capacity.

This method is an O(n) operation, where n is Count.

The following code example shows how to trim the unused portions of the ArrayList and how to clear the values of the ArrayList.

Imports System
Imports System.Collections
Imports Microsoft.VisualBasic

Public Class SamplesArrayList    
    
    Public Shared Sub Main()
        
        ' Creates and initializes a new ArrayList.
        Dim myAL As New ArrayList()
        myAL.Add("The")
        myAL.Add("quick")
        myAL.Add("brown")
        myAL.Add("fox")
        myAL.Add("jumped")
        
        ' Displays the count, capacity and values of the ArrayList.
        Console.WriteLine("Initially,")
        Console.WriteLine("   Count    : {0}", myAL.Count)
        Console.WriteLine("   Capacity : {0}", myAL.Capacity)
        Console.Write("   Values:")
        PrintValues(myAL)
        
        ' Trim the ArrayList.
        myAL.TrimToSize()
        
        ' Displays the count, capacity and values of the ArrayList.
        Console.WriteLine("After TrimToSize,")
        Console.WriteLine("   Count    : {0}", myAL.Count)
        Console.WriteLine("   Capacity : {0}", myAL.Capacity)
        Console.Write("   Values:")
        PrintValues(myAL)
        
        ' Clear the ArrayList.
        myAL.Clear()
        
        ' Displays the count, capacity and values of the ArrayList.
        Console.WriteLine("After Clear,")
        Console.WriteLine("   Count    : {0}", myAL.Count)
        Console.WriteLine("   Capacity : {0}", myAL.Capacity)
        Console.Write("   Values:")
        PrintValues(myAL)
        
        ' Trim the ArrayList again.
        myAL.TrimToSize()
        
        ' Displays the count, capacity and values of the ArrayList.
        Console.WriteLine("After the second TrimToSize,")
        Console.WriteLine("   Count    : {0}", myAL.Count)
        Console.WriteLine("   Capacity : {0}", myAL.Capacity)
        Console.Write("   Values:")
        PrintValues(myAL)
    End Sub

    Public Shared Sub PrintValues(myList As IEnumerable)
        Dim obj As [Object]
        For Each obj In  myList
            Console.Write("   {0}", obj)
        Next obj
        Console.WriteLine()
    End Sub 'PrintValues

End Class

' This code produces the following output.
' 
' Initially,
'    Count    : 5
'    Capacity : 16
'    Values:    The    quick    brown    fox    jumped
' After TrimToSize,
'    Count    : 5
'    Capacity : 5
'    Values:    The    quick    brown    fox    jumped
' After Clear,
'    Count    : 0
'    Capacity : 5
'    Values:
' After the second TrimToSize,
'    Count    : 0
'    Capacity : 16
'    Values:

import System.*;
import System.Collections.*;

public class SamplesArrayList
{
    public static void main(String[] args)
    {
        // Creates and initializes a new ArrayList.
        ArrayList myAL = new ArrayList();

        myAL.Add("The");
        myAL.Add("quick");
        myAL.Add("brown");
        myAL.Add("fox");
        myAL.Add("jumped");

        // Displays the count, capacity and values of the ArrayList.
        Console.WriteLine("Initially,");
        Console.WriteLine("   Count    : {0}", (Int32)myAL.get_Count());
        Console.WriteLine("   Capacity : {0}", (Int32)myAL.get_Capacity());
        Console.Write("   Values:");
        PrintValues(myAL);

        // Trim the ArrayList.
        myAL.TrimToSize();

        // Displays the count, capacity and values of the ArrayList.
        Console.WriteLine("After TrimToSize,");
        Console.WriteLine("   Count    : {0}", (Int32)myAL.get_Count());
        Console.WriteLine("   Capacity : {0}", (Int32)myAL.get_Capacity());
        Console.Write("   Values:");
        PrintValues(myAL);

        // Clear the ArrayList.
        myAL.Clear();

        // Displays the count, capacity and values of the ArrayList.
        Console.WriteLine("After Clear,");
        Console.WriteLine("   Count    : {0}", (Int32)myAL.get_Count());
        Console.WriteLine("   Capacity : {0}", (Int32)myAL.get_Capacity());
        Console.Write("   Values:");
        PrintValues(myAL);

        // Trim the ArrayList again.
        myAL.TrimToSize();

        // Displays the count, capacity and values of the ArrayList.
        Console.WriteLine("After the second TrimToSize,");
        Console.WriteLine("   Count    : {0}", (Int32)myAL.get_Count());
        Console.WriteLine("   Capacity : {0}", (Int32)myAL.get_Capacity());
        Console.Write("   Values:");
        PrintValues(myAL);
    } //main

    public static void PrintValues(IEnumerable myList)
    {
        IEnumerator objMyEnum = myList.GetEnumerator();
        while (objMyEnum.MoveNext()) {
            Object obj = objMyEnum.get_Current();
            Console.Write("   {0}", obj);
        }
        Console.WriteLine();
    } //PrintValues
} //SamplesArrayList 
/* 
 This code produces the following output.
 
 Initially,
    Count    : 5
    Capacity : 16
    Values:    The    quick    brown    fox    jumped
 After TrimToSize,
    Count    : 5
    Capacity : 5
    Values:    The    quick    brown    fox    jumped
 After Clear,
    Count    : 0
    Capacity : 5
    Values:
 After the second TrimToSize,
    Count    : 0
    Capacity : 16
    Values:
 */

import System;
import System.Collections;


// Creates and initializes a new ArrayList.
var myAL : ArrayList = new ArrayList();
myAL.Add( "The" );
myAL.Add( "quick" );
myAL.Add( "brown" );
myAL.Add( "fox" );
myAL.Add( "jumped" );

// Displays the count, capacity and values of the ArrayList.
Console.WriteLine( "Initially," );
Console.WriteLine( "   Count    : {0}", myAL.Count );
Console.WriteLine( "   Capacity : {0}", myAL.Capacity );
Console.Write( "   Values:" );
PrintValues( myAL );

// Trim the ArrayList.
myAL.TrimToSize();

// Displays the count, capacity and values of the ArrayList.
Console.WriteLine( "After TrimToSize," );
Console.WriteLine( "   Count    : {0}", myAL.Count );
Console.WriteLine( "   Capacity : {0}", myAL.Capacity );
Console.Write( "   Values:" );
PrintValues( myAL );

// Clear the ArrayList.
myAL.Clear();

// Displays the count, capacity and values of the ArrayList.
Console.WriteLine( "After Clear," );
Console.WriteLine( "   Count    : {0}", myAL.Count );
Console.WriteLine( "   Capacity : {0}", myAL.Capacity );
Console.Write( "   Values:" );
PrintValues( myAL );

// Trim the ArrayList again.
myAL.TrimToSize();

// Displays the count, capacity and values of the ArrayList.
Console.WriteLine( "After the second TrimToSize," );
Console.WriteLine( "   Count    : {0}", myAL.Count );
Console.WriteLine( "   Capacity : {0}", myAL.Capacity );
Console.Write( "   Values:" );
PrintValues( myAL );
 
function PrintValues( myList : IEnumerable)  {
   var myEnumerator : System.Collections.IEnumerator  = myList.GetEnumerator();
   while ( myEnumerator.MoveNext() )
      Console.Write( "\t{0}", myEnumerator.Current );
   Console.WriteLine();
}
 /* 
 This code produces the following output.
 
 Initially,
    Count    : 5
    Capacity : 16
    Values:    The    quick    brown    fox    jumped
 After TrimToSize,
    Count    : 5
    Capacity : 5
    Values:    The    quick    brown    fox    jumped
 After Clear,
    Count    : 0
    Capacity : 5
    Values:
 After the second TrimToSize,
    Count    : 0
    Capacity : 16
    Values:
 */ 

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

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