String.IsInterned(String) Metode

Definisi

Ruang nama:

System

Rakitan:

netstandard.dll, System.Runtime.dll

Sumber:

String.CoreCLR.cs

Mengambil referensi ke 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

Parameter

str

String

String yang akan dicari di kumpulan magang.

Mengembalikan

String

Referensi ke str jika berada dalam kumpulan magang runtime bahasa umum; jika tidak, null.

Pengecualian

ArgumentNullException

str adalah null.

Contoh

Contoh berikut menunjukkan cara menggunakan IsInterned untuk memeriksa apakah string berada di kumpulan magang dan untuk memverifikasi kesetaraan referensi string magang.

// 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

Keterangan

Runtime bahasa umum secara otomatis mempertahankan tabel, yang disebut kumpulan magang, yang berisi satu instans dari setiap konstanta string harfiah unik yang dideklarasikan dalam program, serta instans unik apa pun yang String Anda tambahkan secara terprogram dengan memanggil Intern metode .

Kumpulan magang menghemat penyimpanan string. Jika Anda menetapkan konstanta string literal ke beberapa variabel, setiap variabel diatur untuk mereferensikan konstanta yang sama di kumpulan magang alih-alih mereferensikan beberapa instans String berbeda yang memiliki nilai yang identik.

Metode ini mencari str di kumpulan magang. Jika str telah diinternasi, referensi ke instans tersebut dikembalikan; jika tidak, null dikembalikan.

Bandingkan metode ini dengan Intern metode .

Metode ini tidak mengembalikan nilai Boolean. Jika Anda memanggil metode karena Anda menginginkan nilai Boolean yang menunjukkan apakah string tertentu diinternasi, Anda dapat menggunakan kode seperti berikut ini.

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.

Lihat juga

• Intern(String)