List<T>.TrimExcess 메서드

정의

List<T>에 있는 요소의 실제 수가 임계값보다 작은 경우 용량을 요소 수로 설정합니다.Sets the capacity to the actual number of elements in the List<T>, if that number is less than a threshold value.

public:
 void TrimExcess();
public void TrimExcess ();
member this.TrimExcess : unit -> unit
Public Sub TrimExcess ()

예제

다음 예제에서는 간단한 비즈니스 개체를 포함 하는 List<T>의 용량과 개수를 확인 하는 방법을 보여 줍니다. TrimExcess 메서드를 사용 하 여 추가 용량을 제거 하는 방법을 보여 줍니다.The following example demonstrates how to check the capacity and count of a List<T> that contains a simple business object, and illustrates using the TrimExcess method to remove extra capacity.

using System;
using System.Collections.Generic;
// Simple business object. A PartId is used to identify a part 
// but the part name be different for the same Id.
public class Part : IEquatable<Part>
{
    public string PartName { get; set; }
    public int PartId { get; set; }
    public override string ToString()
    {
        return "ID: " + PartId + "   Name: " + PartName;
    }
    public override bool Equals(object obj)
    {
        if (obj == null) return false;
        Part objAsPart = obj as Part;
        if (objAsPart == null) return false;
        else return Equals(objAsPart);
    }
    public override int GetHashCode()
    {
        return base.GetHashCode();
    }
    public bool Equals(Part other)
    {
        if (other == null) return false;
        return (this.PartId.Equals(other.PartId));
    }
    // Should also override == and != operators.
}
public class Example
{

    public static void Main()
    {
        List<Part> parts = new List<Part>();

        Console.WriteLine("\nCapacity: {0}", parts.Capacity);

        parts.Add(new Part() { PartName = "crank arm", PartId = 1234 });
        parts.Add(new Part() { PartName = "chain ring", PartId = 1334 });
        parts.Add(new Part() { PartName = "seat", PartId = 1434 });
        parts.Add(new Part() { PartName = "cassette", PartId = 1534 });
        parts.Add(new Part() { PartName = "shift lever", PartId = 1634 }); ;

        Console.WriteLine();
        foreach (Part aPart in parts)
        {
            Console.WriteLine(aPart);
        }

        Console.WriteLine("\nCapacity: {0}", parts.Capacity);
        Console.WriteLine("Count: {0}", parts.Count);

        parts.TrimExcess();
        Console.WriteLine("\nTrimExcess()");
        Console.WriteLine("Capacity: {0}", parts.Capacity);
        Console.WriteLine("Count: {0}", parts.Count);

        parts.Clear();
        Console.WriteLine("\nClear()");
        Console.WriteLine("Capacity: {0}", parts.Capacity);
        Console.WriteLine("Count: {0}", parts.Count);
    }
    /*
     This code example produces the following output. 
            Capacity: 0

            ID: 1234   Name: crank arm
            ID: 1334   Name: chain ring
            ID: 1434   Name: seat
            ID: 1534   Name: cassette
            ID: 1634   Name: shift lever

            Capacity: 8
            Count: 5

            TrimExcess()
            Capacity: 5
            Count: 5

            Clear()
            Capacity: 5
            Count: 0
     */
}
Imports System.Collections.Generic

' Simple business object. A PartId is used to identify a part 
' but the part name can change.
Public Class Part
    Implements IEquatable(Of Part)
    Public Property PartName() As String
        Get
            Return m_PartName
        End Get
        Set(value As String)
            m_PartName = Value
        End Set
    End Property
    Private m_PartName As String
    Public Property PartId() As Integer
        Get
            Return m_PartId
        End Get
        Set(value As Integer)
            m_PartId = Value
        End Set
    End Property
    Private m_PartId As Integer
    Public Overrides Function ToString() As String
        Return "ID: " & PartId & "   Name: " & PartName
    End Function
    Public Overrides Function Equals(obj As Object) As Boolean
        If obj Is Nothing Then
            Return False
        End If
        Dim objAsPart As Part = TryCast(obj, Part)
        If objAsPart Is Nothing Then
            Return False
        Else
            Return Equals(objAsPart)
        End If
    End Function
    Public Overrides Function GetHashCode() As Integer
        Return MyBase.GetHashCode()
    End Function
    Public Overloads Function Equals(other As Part) As Boolean Implements IEquatable(Of Part).Equals
        If other Is Nothing Then
            Return False
        End If
        Return (Me.PartId.Equals(other.PartId))
    End Function
    ' Should also override == and != operators.

End Class
Public Class Example

    Public Shared Sub Main()
        Dim parts As New List(Of Part)()

        Console.WriteLine(vbLf & "Capacity: {0}", parts.Capacity)

        ' Add parts to the list.
        parts.Add(New Part() With { _
             .PartName = "crank arm", _
             .PartId = 1234 _
        })
        parts.Add(New Part() With { _
             .PartName = "chain ring", _
             .PartId = 1334 _
        })
        parts.Add(New Part() With { _
             .PartName = "regular seat", _
             .PartId = 1434 _
        })
        parts.Add(New Part() With { _
             .PartName = "banana seat", _
             .PartId = 1444 _
        })
        parts.Add(New Part() With { _
             .PartName = "cassette", _
             .PartId = 1534 _
        })
        parts.Add(New Part() With { _
             .PartName = "shift lever", _
             .PartId = 1634 _
        })



        Console.WriteLine()
        For Each aPart As Part In parts
            Console.WriteLine(aPart)
        Next

        Console.WriteLine(vbLf & "Capacity: {0}", parts.Capacity)
        Console.WriteLine("Count: {0}", parts.Count)

        parts.TrimExcess()
        Console.WriteLine(vbLf & "TrimExcess()")
        Console.WriteLine("Capacity: {0}", parts.Capacity)
        Console.WriteLine("Count: {0}", parts.Count)

        parts.Clear()
        Console.WriteLine(vbLf & "Clear()")
        Console.WriteLine("Capacity: {0}", parts.Capacity)
        Console.WriteLine("Count: {0}", parts.Count)
    End Sub
    '
    '     This code example produces the following output. 
    '            Capacity: 0
    '
    '            ID: 1234   Name: crank arm
    '            ID: 1334   Name: chain ring
    '            ID: 1434   Name: seat
    '            ID: 1534   Name: cassette
    '            ID: 1634   Name: shift lever
    '
    '            Capacity: 8
    '            Count: 6
    '
    '            TrimExcess()
    '            Capacity: 6
    '            Count: 6
    '
    '            Clear()
    '            Capacity: 6
    '            Count: 0
    '     

End Class

다음 예제는 TrimExcess 메서드.The following example demonstrates the TrimExcess method. List<T> 클래스의 여러 속성 및 메서드는 문자열 목록에서 항목을 추가, 삽입 및 제거 하는 데 사용 됩니다.Several properties and methods of the List<T> class are used to add, insert, and remove items from a list of strings. 그런 다음 TrimExcess 메서드를 사용 하 여 개수에 맞게 용량을 줄이고 CapacityCount 속성을 표시 합니다.Then the TrimExcess method is used to reduce the capacity to match the count, and the Capacity and Count properties are displayed. 총 용량을 10% 미만 사용 하지 않은 용량이, 하는 경우 목록은 하지 크기가 조정 되었습니다.If the unused capacity had been less than 10 percent of total capacity, the list would not have been resized. 마지막으로, 목록의 내용은 지워집니다.Finally, the contents of the list are cleared.

using namespace System;
using namespace System::Collections::Generic;

void main()
{
    List<String^>^ dinosaurs = gcnew List<String^>();

    Console::WriteLine("\nCapacity: {0}", dinosaurs->Capacity);

    dinosaurs->Add("Tyrannosaurus");
    dinosaurs->Add("Amargasaurus");
    dinosaurs->Add("Mamenchisaurus");
    dinosaurs->Add("Deinonychus");
    dinosaurs->Add("Compsognathus");

    Console::WriteLine();
    for each(String^ dinosaur in dinosaurs )
    {
        Console::WriteLine(dinosaur);
    }

    Console::WriteLine("\nCapacity: {0}", dinosaurs->Capacity);
    Console::WriteLine("Count: {0}", dinosaurs->Count);

    Console::WriteLine("\nContains(\"Deinonychus\"): {0}",
        dinosaurs->Contains("Deinonychus"));

    Console::WriteLine("\nInsert(2, \"Compsognathus\")");
    dinosaurs->Insert(2, "Compsognathus");

    Console::WriteLine();
    for each(String^ dinosaur in dinosaurs )
    {
        Console::WriteLine(dinosaur);
    }

    Console::WriteLine("\ndinosaurs[3]: {0}", dinosaurs[3]);

    Console::WriteLine("\nRemove(\"Compsognathus\")");
    dinosaurs->Remove("Compsognathus");

    Console::WriteLine();
    for each(String^ dinosaur in dinosaurs )
    {
        Console::WriteLine(dinosaur);
    }

    dinosaurs->TrimExcess();
    Console::WriteLine("\nTrimExcess()");
    Console::WriteLine("Capacity: {0}", dinosaurs->Capacity);
    Console::WriteLine("Count: {0}", dinosaurs->Count);

    dinosaurs->Clear();
    Console::WriteLine("\nClear()");
    Console::WriteLine("Capacity: {0}", dinosaurs->Capacity);
    Console::WriteLine("Count: {0}", dinosaurs->Count);
}

/* This code example produces the following output:

Capacity: 0

Tyrannosaurus
Amargasaurus
Mamenchisaurus
Deinonychus
Compsognathus

Capacity: 8
Count: 5

Contains("Deinonychus"): True

Insert(2, "Compsognathus")

Tyrannosaurus
Amargasaurus
Compsognathus
Mamenchisaurus
Deinonychus
Compsognathus

dinosaurs[3]: Mamenchisaurus

Remove("Compsognathus")

Tyrannosaurus
Amargasaurus
Mamenchisaurus
Deinonychus
Compsognathus

TrimExcess()
Capacity: 5
Count: 5

Clear()
Capacity: 5
Count: 0
 */
List<string> dinosaurs = new List<string>();

Console.WriteLine("\nCapacity: {0}", dinosaurs.Capacity);

dinosaurs.Add("Tyrannosaurus");
dinosaurs.Add("Amargasaurus");
dinosaurs.Add("Mamenchisaurus");
dinosaurs.Add("Deinonychus");
dinosaurs.Add("Compsognathus");
Console.WriteLine();
foreach(string dinosaur in dinosaurs)
{
    Console.WriteLine(dinosaur);
}

Console.WriteLine("\nCapacity: {0}", dinosaurs.Capacity);
Console.WriteLine("Count: {0}", dinosaurs.Count);

Console.WriteLine("\nContains(\"Deinonychus\"): {0}",
    dinosaurs.Contains("Deinonychus"));

Console.WriteLine("\nInsert(2, \"Compsognathus\")");
dinosaurs.Insert(2, "Compsognathus");

Console.WriteLine();
foreach(string dinosaur in dinosaurs)
{
    Console.WriteLine(dinosaur);
}

// Shows accessing the list using the Item property.
Console.WriteLine("\ndinosaurs[3]: {0}", dinosaurs[3]);

Console.WriteLine("\nRemove(\"Compsognathus\")");
dinosaurs.Remove("Compsognathus");

Console.WriteLine();
foreach(string dinosaur in dinosaurs)
{
    Console.WriteLine(dinosaur);
}

dinosaurs.TrimExcess();
Console.WriteLine("\nTrimExcess()");
Console.WriteLine("Capacity: {0}", dinosaurs.Capacity);
Console.WriteLine("Count: {0}", dinosaurs.Count);

dinosaurs.Clear();
Console.WriteLine("\nClear()");
Console.WriteLine("Capacity: {0}", dinosaurs.Capacity);
Console.WriteLine("Count: {0}", dinosaurs.Count);

/* This code example produces the following output:

Capacity: 0

Tyrannosaurus
Amargasaurus
Mamenchisaurus
Deinonychus
Compsognathus

Capacity: 8
Count: 5

Contains("Deinonychus"): True

Insert(2, "Compsognathus")

Tyrannosaurus
Amargasaurus
Compsognathus
Mamenchisaurus
Deinonychus
Compsognathus

dinosaurs[3]: Mamenchisaurus

Remove("Compsognathus")

Tyrannosaurus
Amargasaurus
Mamenchisaurus
Deinonychus
Compsognathus

TrimExcess()
Capacity: 5
Count: 5

Clear()
Capacity: 5
Count: 0
 */
Imports System.Collections.Generic

Public Class Example

    Public Shared Sub Main()
        Dim dinosaurs As New List(Of String)

        Console.WriteLine(vbLf & "Capacity: {0}", dinosaurs.Capacity)

        dinosaurs.Add("Tyrannosaurus")
        dinosaurs.Add("Amargasaurus")
        dinosaurs.Add("Mamenchisaurus")
        dinosaurs.Add("Deinonychus")
        dinosaurs.Add("Compsognathus")

        Console.WriteLine()
        For Each dinosaur As String In dinosaurs
            Console.WriteLine(dinosaur)
        Next

        Console.WriteLine(vbLf & "Capacity: {0}", dinosaurs.Capacity)
        Console.WriteLine("Count: {0}", dinosaurs.Count)

        Console.WriteLine(vbLf & "Contains(""Deinonychus""): {0}", _
            dinosaurs.Contains("Deinonychus"))

        Console.WriteLine(vbLf & "Insert(2, ""Compsognathus"")")
        dinosaurs.Insert(2, "Compsognathus")

        Console.WriteLine()
        For Each dinosaur As String In dinosaurs
            Console.WriteLine(dinosaur)
        Next
        ' Shows how to access the list using the Item property.
        Console.WriteLine(vbLf & "dinosaurs(3): {0}", dinosaurs(3))
        Console.WriteLine(vbLf & "Remove(""Compsognathus"")")
        dinosaurs.Remove("Compsognathus")

        Console.WriteLine()
        For Each dinosaur As String In dinosaurs
            Console.WriteLine(dinosaur)
        Next

        dinosaurs.TrimExcess()
        Console.WriteLine(vbLf & "TrimExcess()")
        Console.WriteLine("Capacity: {0}", dinosaurs.Capacity)
        Console.WriteLine("Count: {0}", dinosaurs.Count)

        dinosaurs.Clear()
        Console.WriteLine(vbLf & "Clear()")
        Console.WriteLine("Capacity: {0}", dinosaurs.Capacity)
        Console.WriteLine("Count: {0}", dinosaurs.Count)
    End Sub
End Class

' This code example produces the following output:
'
'Capacity: 0
'
'Tyrannosaurus
'Amargasaurus
'Mamenchisaurus
'Deinonychus
'Compsognathus
'
'Capacity: 8
'Count: 5
'
'Contains("Deinonychus"): True
'
'Insert(2, "Compsognathus")
'
'Tyrannosaurus
'Amargasaurus
'Compsognathus
'Mamenchisaurus
'Deinonychus
'Compsognathus
'
'dinosaurs(3): Mamenchisaurus
'
'Remove("Compsognathus")
'
'Tyrannosaurus
'Amargasaurus
'Mamenchisaurus
'Deinonychus
'Compsognathus
'
'TrimExcess()
'Capacity: 5
'Count: 5
'
'Clear()
'Capacity: 5
'Count: 0

[<EntryPoint>]
let main argv = 
    // We refer to System.Collections.Generic.List<'T> by its type 
    // abbreviation ResizeArray<'T> to avoid conflict with the List module.    
    // Note: In F# code, F# linked lists are usually preferred over
    // ResizeArray<'T> when an extendable collection is required.
    let dinosaurs = ResizeArray<_>()
 
    // Write out the dinosaurs in the ResizeArray.
    let printDinosaurs() =
        printfn ""
        dinosaurs |> Seq.iter (fun p -> printfn "%O" p) 
 
    
    printfn "\nCapacity: %i" dinosaurs.Capacity
 
    dinosaurs.Add("Tyrannosaurus")
    dinosaurs.Add("Amargasaurus")
    dinosaurs.Add("Mamenchisaurus")
    dinosaurs.Add("Deinonychus")
    dinosaurs.Add("Compsognathus")
 
    printDinosaurs()
 
    printfn "\nCapacity: %i" dinosaurs.Capacity
    printfn "Count: %i" dinosaurs.Count
 
    printfn "\nContains(\"Deinonychus\"): %b" (dinosaurs.Contains("Deinonychus"))
 
    printfn "\nInsert(2, \"Compsognathus\")"
    dinosaurs.Insert(2, "Compsognathus")
 
    printDinosaurs()
 
    // Shows accessing the list using the Item property.
    printfn "\ndinosaurs[3]: %s" dinosaurs.[3]
 
    printfn "\nRemove(\"Compsognathus\")"
    dinosaurs.Remove("Compsognathus") |> ignore
 
    printDinosaurs()
 
    dinosaurs.TrimExcess()
    printfn "\nTrimExcess()"
    printfn "Capacity: %i" dinosaurs.Capacity
    printfn "Count: %i" dinosaurs.Count
 
    dinosaurs.Clear()
    printfn "\nClear()"
    printfn "Capacity: %i" dinosaurs.Capacity
    printfn "Count: %i" dinosaurs.Count
 
    0 // return an integer exit code
 
    (* This code example produces the following output:
 
Capacity: 0
 
Tyrannosaurus
Amargasaurus
Mamenchisaurus
Deinonychus
Compsognathus
 
Capacity: 8
Count: 5
 
Contains("Deinonychus"): true
 
Insert(2, "Compsognathus")
 
Tyrannosaurus
Amargasaurus
Compsognathus
Mamenchisaurus
Deinonychus
Compsognathus
 
dinosaurs[3]: Mamenchisaurus
 
Remove("Compsognathus")
 
Tyrannosaurus
Amargasaurus
Mamenchisaurus
Deinonychus
Compsognathus
 
TrimExcess()
Capacity: 5
Count: 5
 
Clear()
Capacity: 5
Count: 0
    *)

설명

이 메서드는 새 요소가 컬렉션에 추가 될 경우 컬렉션의 메모리 오버 헤드를 최소화할 데 사용할 수 있습니다.This method can be used to minimize a collection's memory overhead if no new elements will be added to the collection. 그러나 큰 List<T>를 재할당 하 고 복사 하는 비용은 상당히 클 수 있으므로 목록이 90%를 초과 하는 경우 TrimExcess 메서드는 아무 작업도 수행 하지 않습니다.The cost of reallocating and copying a large List<T> can be considerable, however, so the TrimExcess method does nothing if the list is at more than 90 percent of capacity. 이 비교적 작은 이익을 얻기에 대 한 큰 재할당 비용을 방지 합니다.This avoids incurring a large reallocation cost for a relatively small gain.

참고

현재 임계값을 90%는 이후 릴리스에서 변경 될 수 있습니다.The current threshold of 90 percent might change in future releases.

이 메서드는 O (n) 작업입니다. 여기서 nCount입니다.This method is an O(n) operation, where n is Count.

List<T>를 초기 상태로 다시 설정 하려면 TrimExcess 메서드를 호출 하기 전에 Clear 메서드를 호출 합니다.To reset a List<T> to its initial state, call the Clear method before calling the TrimExcess method. List<T>을 잘라서 List<T>의 용량을 기본 용량으로 설정 합니다.Trimming an empty List<T> sets the capacity of the List<T> to the default capacity.

Capacity 속성을 사용 하 여 용량을 설정할 수도 있습니다.The capacity can also be set using the Capacity property.

적용 대상

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