Stack<T>.Clear Método

Definição

Remove todos os objetos da Stack<T>.Removes all objects from the Stack<T>.

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

Exemplos

O exemplo de código a seguir demonstra vários métodos da Stack<T> classe genérica, incluindo o Clear método.The following code example demonstrates several methods of the Stack<T> generic class, including the Clear method.

O exemplo de código cria uma pilha de cadeias de caracteres com capacidade padrão e usa o Push método para enviar por push cinco cadeias de caracteres para a pilha.The code example creates a stack of strings with default capacity and uses the Push method to push five strings onto the stack. Os elementos da pilha são enumerados, o que não altera o estado da pilha.The elements of the stack are enumerated, which does not change the state of the stack. O Pop método é usado para retirar a primeira cadeia de caracteres da pilha.The Pop method is used to pop the first string off the stack. O Peek método é usado para examinar o próximo item na pilha e, em seguida, o Pop método é usado para desativá-lo.The Peek method is used to look at the next item on the stack, and then the Pop method is used to pop it off.

O ToArray método é usado para criar uma matriz e copiar os elementos da pilha para ela, então a matriz é passada para o Stack<T> Construtor que usa IEnumerable<T> , criando uma cópia da pilha com a ordem dos elementos invertidos.The ToArray method is used to create an array and copy the stack elements to it, then the array is passed to the Stack<T> constructor that takes IEnumerable<T>, creating a copy of the stack with the order of the elements reversed. Os elementos da cópia são exibidos.The elements of the copy are displayed.

Uma matriz duas vezes o tamanho da pilha é criado e o CopyTo método é usado para copiar os elementos da matriz que começam no meio da matriz.An array twice the size of the stack is created, and the CopyTo method is used to copy the array elements beginning at the middle of the array. O Stack<T> Construtor é usado novamente para criar uma cópia da pilha com a ordem dos elementos invertido; portanto, os três elementos nulos estão no final.The Stack<T> constructor is used again to create a copy of the stack with the order of elements reversed; thus, the three null elements are at the end.

O Contains método é usado para mostrar que a cadeia de caracteres "quatro" está na primeira cópia da pilha, após a qual o Clear método limpa a cópia e a Count Propriedade mostra que a pilha está vazia.The Contains method is used to show that the string "four" is in the first copy of the stack, after which the Clear method clears the copy and the Count property shows that the stack is empty.

using System;
using System.Collections.Generic;

class Example
{
    public static void Main()
    {
        Stack<string> numbers = new Stack<string>();
        numbers.Push("one");
        numbers.Push("two");
        numbers.Push("three");
        numbers.Push("four");
        numbers.Push("five");

        // A stack can be enumerated without disturbing its contents.
        foreach( string number in numbers )
        {
            Console.WriteLine(number);
        }

        Console.WriteLine("\nPopping '{0}'", numbers.Pop());
        Console.WriteLine("Peek at next item to destack: {0}",
            numbers.Peek());
        Console.WriteLine("Popping '{0}'", numbers.Pop());

        // Create a copy of the stack, using the ToArray method and the
        // constructor that accepts an IEnumerable<T>.
        Stack<string> stack2 = new Stack<string>(numbers.ToArray());

        Console.WriteLine("\nContents of the first copy:");
        foreach( string number in stack2 )
        {
            Console.WriteLine(number);
        }

        // Create an array twice the size of the stack and copy the
        // elements of the stack, starting at the middle of the
        // array.
        string[] array2 = new string[numbers.Count * 2];
        numbers.CopyTo(array2, numbers.Count);

        // Create a second stack, using the constructor that accepts an
        // IEnumerable(Of T).
        Stack<string> stack3 = new Stack<string>(array2);

        Console.WriteLine("\nContents of the second copy, with duplicates and nulls:");
        foreach( string number in stack3 )
        {
            Console.WriteLine(number);
        }

        Console.WriteLine("\nstack2.Contains(\"four\") = {0}",
            stack2.Contains("four"));

        Console.WriteLine("\nstack2.Clear()");
        stack2.Clear();
        Console.WriteLine("\nstack2.Count = {0}", stack2.Count);
    }
}

/* This code example produces the following output:

five
four
three
two
one

Popping 'five'
Peek at next item to destack: four
Popping 'four'

Contents of the first copy:
one
two
three

Contents of the second copy, with duplicates and nulls:
one
two
three




stack2.Contains("four") = False

stack2.Clear()

stack2.Count = 0
 */
Imports System.Collections.Generic

Module Example

    Sub Main

        Dim numbers As New Stack(Of String)
        numbers.Push("one")
        numbers.Push("two")
        numbers.Push("three")
        numbers.Push("four")
        numbers.Push("five")

        ' A stack can be enumerated without disturbing its contents.
        For Each number As String In numbers
            Console.WriteLine(number)
        Next

        Console.WriteLine(vbLf & "Popping '{0}'", numbers.Pop())
        Console.WriteLine("Peek at next item to pop: {0}", _
            numbers.Peek())    
        Console.WriteLine("Popping '{0}'", numbers.Pop())

        ' Create another stack, using the ToArray method and the
        ' constructor that accepts an IEnumerable(Of T). Note that
        ' the order of items on the new stack is reversed.
        Dim stack2 As New Stack(Of String)(numbers.ToArray())

        Console.WriteLine(vbLf & "Contents of the first copy:")
        For Each number As String In stack2
            Console.WriteLine(number)
        Next
        
        ' Create an array twice the size of the stack, compensating
        ' for the fact that Visual Basic allocates an extra array 
        ' element. Copy the elements of the stack, starting at the
        ' middle of the array. 
        Dim array2((numbers.Count * 2) - 1) As String
        numbers.CopyTo(array2, numbers.Count)
        
        ' Create a second stack, using the constructor that accepts an
        ' IEnumerable(Of T). The elements are reversed, with the null
        ' elements appearing at the end of the stack when enumerated.
        Dim stack3 As New Stack(Of String)(array2)

        Console.WriteLine(vbLf & _
            "Contents of the second copy, with duplicates and nulls:")
        For Each number As String In stack3
            Console.WriteLine(number)
        Next

        Console.WriteLine(vbLf & "stack2.Contains(""four"") = {0}", _
            stack2.Contains("four"))

        Console.WriteLine(vbLf & "stack2.Clear()")
        stack2.Clear()
        Console.WriteLine(vbLf & "stack2.Count = {0}", _
            stack2.Count)
    End Sub
End Module

' This code example produces the following output:
'
'five
'four
'three
'two
'one
'
'Popping 'five'
'Peek at next item to pop: four
'Popping 'four'
'
'Contents of the first copy:
'one
'two
'three
'
'Contents of the second copy, with duplicates and nulls:
'one
'two
'three
'
'
'
'
'stack2.Contains("four") = False
'
'stack2.Clear()
'
'stack2.Count = 0

Comentários

Count está definido como zero, e referências a outros objetos a partir de elementos da coleção também são liberados.Count is set to zero, and references to other objects from elements of the collection are also released.

A capacidade permanece inalterada.The capacity remains unchanged. Para redefinir a capacidade da Stack<T> chamada, chame TrimExcess .To reset the capacity of the Stack<T>, call TrimExcess. Cortar um vazio Stack<T> define a capacidade do Stack<T> para a capacidade padrão.Trimming an empty Stack<T> sets the capacity of the Stack<T> to the default capacity.

Este método é uma operação O(n), em que n é Count.This method is an O(n) operation, where n is Count.

Aplica-se a