ArrayList.TrimToSize Metodo

Definizione

Spazio dei nomi:

System.Collections

Assembly:

System.Runtime.dll

Source:

ArrayList.cs

Imposta la capacità sul numero effettivo di elementi contenuti in ArrayList.

public:
 virtual void TrimToSize();

public virtual void TrimToSize ();

abstract member TrimToSize : unit -> unit
override this.TrimToSize : unit -> unit

Public Overridable Sub TrimToSize ()

Eccezioni

NotSupportedException

La classe ArrayList è di sola lettura.

-oppure-

Le dimensioni dell'oggetto ArrayList sono fisse.

Esempio

Nell'esempio di codice seguente viene illustrato come tagliare le parti inutilizzate di ArrayList e come cancellare i valori di ArrayList.

using namespace System;
using namespace System::Collections;
void PrintValues( IEnumerable^ myList );
int main()
{
   
   // Creates and initializes a new ArrayList.
   ArrayList^ myAL = gcnew ArrayList;
   myAL->Add( "The" );
   myAL->Add( "quick" );
   myAL->Add( "brown" );
   myAL->Add( "fox" );
   myAL->Add( "jumps" );
   
   // 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 );
}

void PrintValues( IEnumerable^ myList )
{
   IEnumerator^ myEnum = myList->GetEnumerator();
   while ( myEnum->MoveNext() )
   {
      Object^ obj = safe_cast<Object^>(myEnum->Current);
      Console::Write( "   {0}", obj );
   }

   Console::WriteLine();
}

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

using System;
using System.Collections;
public class SamplesArrayList  {

   public static void Main()  {

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

      // 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 );
   }

   public static void PrintValues( IEnumerable myList )  {
      foreach ( Object obj in myList )
         Console.Write( "   {0}", obj );
      Console.WriteLine();
   }
}
/*
This code produces the following output.

Initially,
   Count    : 5
   Capacity : 16
   Values:    The    quick    brown    fox    jumps
After TrimToSize,
   Count    : 5
   Capacity : 5
   Values:    The    quick    brown    fox    jumps
After Clear,
   Count    : 0
   Capacity : 5
   Values:
After the second TrimToSize,
   Count    : 0
   Capacity : 16
   Values:
*/

Imports System.Collections

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("jumps")
        
        ' 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

End Class

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

Commenti

Questo metodo può essere usato per ridurre al minimo l'overhead di memoria di una raccolta se non verranno aggiunti nuovi elementi alla raccolta.

Per reimpostare lo stato iniziale di un ArrayList oggetto , chiamare il Clear metodo prima di chiamare TrimToSize. Se si taglia un oggetto vuoto ArrayList , la capacità di viene ArrayList impostata sulla capacità predefinita.

Questo metodo è un'operazione O(n) , dove n è Count.

Vedi anche

• Clear()
• Capacity
• Count