Queue<T>.Clear Metodo

Definizione

Rimuove tutti gli oggetti da Queue<T>.Removes all objects from the Queue<T>.

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

Esempio

Nell'esempio di codice seguente vengono illustrati diversi metodi della Queue<T> classe generica, incluso il Clear metodo.The following code example demonstrates several methods of the Queue<T> generic class, including the Clear method.

Nell'esempio di codice viene creata una coda di stringhe con la capacità predefinita e viene utilizzato il Enqueue metodo per accodare cinque stringhe.The code example creates a queue of strings with default capacity and uses the Enqueue method to queue five strings. Gli elementi della coda vengono enumerati, che non modifica lo stato della coda.The elements of the queue are enumerated, which does not change the state of the queue. Il Dequeue metodo viene usato per rimuovere dalla coda la prima stringa.The Dequeue method is used to dequeue the first string. Il Peek metodo viene usato per esaminare l'elemento successivo nella coda e quindi il Dequeue metodo viene usato per rimuovere la coda.The Peek method is used to look at the next item in the queue, and then the Dequeue method is used to dequeue it.

Il ToArray metodo viene usato per creare una matrice e copiarvi gli elementi della coda, quindi la matrice viene passata al Queue<T> costruttore che accetta IEnumerable<T> , creando una copia della coda.The ToArray method is used to create an array and copy the queue elements to it, then the array is passed to the Queue<T> constructor that takes IEnumerable<T>, creating a copy of the queue. Vengono visualizzati gli elementi della copia.The elements of the copy are displayed.

Viene creata una matrice due volte la dimensione della coda e il CopyTo metodo viene usato per copiare gli elementi della matrice a partire dal centro della matrice.An array twice the size of the queue is created, and the CopyTo method is used to copy the array elements beginning at the middle of the array. Il Queue<T> costruttore viene nuovamente utilizzato per creare una seconda copia della coda contenente tre elementi null all'inizio.The Queue<T> constructor is used again to create a second copy of the queue containing three null elements at the beginning.

Il Contains metodo viene utilizzato per indicare che la stringa "quattro" si trova nella prima copia della coda, dopo la quale il Clear metodo cancella la copia e la Count proprietà indica che la coda è vuota.The Contains method is used to show that the string "four" is in the first copy of the queue, after which the Clear method clears the copy and the Count property shows that the queue is empty.

using System;
using System.Collections.Generic;

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

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

        Console.WriteLine("\nDequeuing '{0}'", numbers.Dequeue());
        Console.WriteLine("Peek at next item to dequeue: {0}",
            numbers.Peek());
        Console.WriteLine("Dequeuing '{0}'", numbers.Dequeue());

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

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

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

        // Create a second queue, using the constructor that accepts an
        // IEnumerable(Of T).
        Queue<string> queueCopy2 = new Queue<string>(array2);

        Console.WriteLine("\nContents of the second copy, with duplicates and nulls:");
        foreach( string number in queueCopy2 )
        {
            Console.WriteLine(number);
        }

        Console.WriteLine("\nqueueCopy.Contains(\"four\") = {0}",
            queueCopy.Contains("four"));

        Console.WriteLine("\nqueueCopy.Clear()");
        queueCopy.Clear();
        Console.WriteLine("\nqueueCopy.Count = {0}", queueCopy.Count);
    }
}

/* This code example produces the following output:

one
two
three
four
five

Dequeuing 'one'
Peek at next item to dequeue: two
Dequeuing 'two'

Contents of the copy:
three
four
five

Contents of the second copy, with duplicates and nulls:



three
four
five

queueCopy.Contains("four") = True

queueCopy.Clear()

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

Module Example

    Sub Main

        Dim numbers As New Queue(Of String)
        numbers.Enqueue("one")
        numbers.Enqueue("two")
        numbers.Enqueue("three")
        numbers.Enqueue("four")
        numbers.Enqueue("five")

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

        Console.WriteLine(vbLf & "Dequeuing '{0}'", numbers.Dequeue())
        Console.WriteLine("Peek at next item to dequeue: {0}", _
            numbers.Peek())    
        Console.WriteLine("Dequeuing '{0}'", numbers.Dequeue())

        ' Create a copy of the queue, using the ToArray method and the
        ' constructor that accepts an IEnumerable(Of T).
        Dim queueCopy As New Queue(Of String)(numbers.ToArray())

        Console.WriteLine(vbLf & "Contents of the first copy:")
        For Each number As String In queueCopy
            Console.WriteLine(number)
        Next
        
        ' Create an array twice the size of the queue, compensating
        ' for the fact that Visual Basic allocates an extra array 
        ' element. Copy the elements of the queue, starting at the
        ' middle of the array. 
        Dim array2((numbers.Count * 2) - 1) As String
        numbers.CopyTo(array2, numbers.Count)
        
        ' Create a second queue, using the constructor that accepts an
        ' IEnumerable(Of T).
        Dim queueCopy2 As New Queue(Of String)(array2)

        Console.WriteLine(vbLf & _
            "Contents of the second copy, with duplicates and nulls:")
        For Each number As String In queueCopy2
            Console.WriteLine(number)
        Next

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

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

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

Commenti

Count è impostato su zero e vengono rilasciati anche i riferimenti ad altri oggetti da elementi della raccolta.Count is set to zero, and references to other objects from elements of the collection are also released.

La capacità rimane invariata.The capacity remains unchanged. Per reimpostare la capacità di Queue<T> , chiamare TrimExcess .To reset the capacity of the Queue<T>, call TrimExcess. Il taglio di un oggetto vuoto Queue<T> imposta la capacità di sulla Queue<T> capacità predefinita.Trimming an empty Queue<T> sets the capacity of the Queue<T> to the default capacity.

Questo metodo è un'operazione O ( n ), dove n è Count .This method is an O(n) operation, where n is Count.

Si applica a

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