String.IsInterned(String) Método

Definição

Namespace:

System

Assemblies:

netstandard.dll, System.Runtime.dll

Origem:

String.CoreCLR.cs

Recupera uma referência a um especificado String.

public:
 static System::String ^ IsInterned(System::String ^ str);

public static string? IsInterned(string str);

static member IsInterned : string -> string

Public Shared Function IsInterned (str As String) As String

Parâmetros

str

String

A cadeia de caracteres a ser pesquisada no pool de estagiários.

Retornos

String

Uma referência para str se ele estiver no pool de estagiários do Common Language Runtime; caso contrário, null.

Exceções

ArgumentNullException

str é null.

Exemplos

O exemplo a seguir demonstra como usar IsInterned para verificar se as cadeias de caracteres estão no pool de estagiários e verificar a igualdade de referência de cadeias de caracteres internadas.

// Sample for String.IsInterned(String)
using System;
using System.Text;

class Sample
{
    public static void Main()
    {
        // Constructed strings are not automatically interned.
        string s1 = new StringBuilder().Append("My").Append("Test").ToString();
        string s2 = new StringBuilder().Append("My").Append("Test").ToString();

        // Neither string is in the intern pool yet.
        Console.WriteLine($"Is s1 interned? {String.IsInterned(s1) != null}");
        Console.WriteLine($"Is s2 interned? {String.IsInterned(s2) != null}");

        // Intern s1 explicitly.
        string i1 = String.Intern(s1);

        // Now s2 can be found in the intern pool.
        string i2 = String.IsInterned(s2);

        Console.WriteLine($"Is s2 interned after interning s1? {i2 != null}");
        Console.WriteLine($"Are i1 and i2 the same reference? {Object.ReferenceEquals(i1, i2)}");
    }
}

// This example produces the following results:
//
// Is s1 interned? False
// Is s2 interned? False
// Is s2 interned after interning s1? True
// Are i1 and i2 the same reference? True

// Sample for String.IsInterned(String)
open System
open System.Text

// Constructed strings are not automatically interned.
let s1 = StringBuilder().Append("My").Append("Test").ToString()
let s2 = StringBuilder().Append("My").Append("Test").ToString()

// Neither string is in the intern pool yet.
printfn $"Is s1 interned? {String.IsInterned(s1) <> null}"
printfn $"Is s2 interned? {String.IsInterned(s2) <> null}"

// Intern s1 explicitly.
let i1 = String.Intern(s1)

// Now s2 can be found in the intern pool.
let i2 = String.IsInterned(s2)

printfn $"Is s2 interned after interning s1? {i2 <> null}"
printfn $"Are i1 and i2 the same reference? {Object.ReferenceEquals(i1, i2)}"

// This example produces the following results:
//
// Is s1 interned? False
// Is s2 interned? False
// Is s2 interned after interning s1? True
// Are i1 and i2 the same reference? True

' Constructed strings are not automatically interned.
Dim s1 As String = New StringBuilder().Append("My").Append("Test").ToString()
Dim s2 As String = New StringBuilder().Append("My").Append("Test").ToString()

' Neither string is in the intern pool yet.
Console.WriteLine($"Is s1 interned? {String.IsInterned(s1) IsNot Nothing}")
Console.WriteLine($"Is s2 interned? {String.IsInterned(s2) IsNot Nothing}")

' Intern s1 explicitly.
Dim i1 As String = String.Intern(s1)

' Now s2 can be found in the intern pool.
Dim i2 As String = String.IsInterned(s2)

Console.WriteLine($"Is s2 interned after interning s1? {i2 IsNot Nothing}")
Console.WriteLine($"Are i1 and i2 the same reference? {Object.ReferenceEquals(i1, i2)}")

' This example produces the following results:
'
' Is s1 interned? False
' Is s2 interned? False
' Is s2 interned after interning s1? True
' Are i1 and i2 the same reference? True

Comentários

O common language runtime mantém automaticamente uma tabela, chamada de pool de estagiários, que contém uma única instância de cada constante de cadeia de caracteres literal exclusiva declarada em um programa, bem como qualquer instância exclusiva de String você adicionar programaticamente chamando o Intern método.

O pool de estagiários conserva o armazenamento de cadeias de caracteres. Se você atribuir uma constante de cadeia de caracteres literal a várias variáveis, cada variável será definida para fazer referência à mesma constante no pool de estagiários em vez de referenciar várias instâncias diferentes com String valores idênticos.

Esse método pesquisa str no pool de estagiários. Se str já tiver sido internada, uma referência a essa instância será retornada; caso contrário, null será retornada.

Compare esse método com o Intern método.

Esse método não retorna um valor booliano. Se você chamar o método porque deseja um valor booliano que indique se uma cadeia de caracteres específica está internada, você pode usar código como o seguinte.

using System;

public class Example
{
   public static void Main()
   {
      string str1 = "a";
      string str2 = str1 + "b";
      string str3 = str2 + "c";
      string[] strings = { "value", "part1" + "_" + "part2", str3, 
                           String.Empty, null };
      foreach (var value in strings) {
         if (value == null) continue;
         
         bool interned = String.IsInterned(value) != null;
         if (interned)
            Console.WriteLine("'{0}' is in the string intern pool.", 
                              value);
         else
            Console.WriteLine("'{0}' is not in the string intern pool.",
                              value);                      
      }
   }
}
// The example displays the following output:
//       'value' is in the string intern pool.
//       'part1_part2' is in the string intern pool.
//       'abc' is not in the string intern pool.
//       '' is in the string intern pool.

open System

let str1 = "a"
let str2 = str1 + "b"
let str3 = str2 + "c"
let strings = 
    [| "value"; "part1" + "_" + "part2"; str3
       String.Empty; null |]
for value in strings do
    if value <> null then
        let interned = String.IsInterned(value) <> null
        if interned then
            printfn $"'{value}' is in the string intern pool."
        else
            printfn $"'{value}' is not in the string intern pool."
// The example displays the following output:
//       'value' is in the string intern pool.
//       'part1_part2' is in the string intern pool.
//       'abc' is not in the string intern pool.
//       '' is in the string intern pool.

Dim str1 As String = "a"
Dim str2 As String = str1 + "b"
Dim str3 As String = str2 + "c"
Dim strings() As String = {"value", "part1" + "_" + "part2", str3,
                            String.Empty, Nothing}
For Each value In strings
    If value Is Nothing Then Continue For

    Dim interned As Boolean = (String.IsInterned(value) IsNot Nothing)
    If interned Then
        Console.WriteLine($"'{value}' is in the string intern pool.")
    Else
        Console.WriteLine($"'{value}' is not in the string intern pool.")
    End If
Next

' The example displays the following output:
'       'value' is in the string intern pool.
'       'part1_part2' is in the string intern pool.
'       'abc' is not in the string intern pool.
'       '' is in the string intern pool.

Confira também

• Intern(String)