ArrayList.TrimToSize Metodo
Importante
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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 ()
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:
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.
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