ArrayList.IsSynchronized プロパティ

定義

ArrayList へのアクセスが同期されている (スレッド セーフである) かどうかを示す値を取得します。Gets a value indicating whether access to the ArrayList is synchronized (thread safe).

public:
 virtual property bool IsSynchronized { bool get(); };
public virtual bool IsSynchronized { get; }
member this.IsSynchronized : bool
Public Overridable ReadOnly Property IsSynchronized As Boolean

プロパティ値

true へのアクセスが同期されている (スレッド セーフである) 場合は ArrayList 。それ以外の場合は falsetrue if access to the ArrayList is synchronized (thread safe); otherwise, false. 既定値は、false です。The default is false.

実装

次のコード例は、列挙体全体の中で SyncRoot を使用してコレクションをロックする方法を示しています。The following code example shows how to lock the collection using the SyncRoot during the entire enumeration.

ArrayList^ myCollection = gcnew ArrayList();
bool lockTaken = false;
try
{
    Monitor::Enter(myCollection->SyncRoot, lockTaken);
    for each (Object^ item in myCollection);
    {
        // Insert your code here.
    }
}
finally
{
    if (lockTaken)
    {
        Monitor::Exit(myCollection->SyncRoot);
    }
}
ArrayList myCollection = new ArrayList();

lock(myCollection.SyncRoot)
{
    foreach (object item in myCollection)
    {
        // Insert your code here.
    }
}
Dim myCollection As New ArrayList()

SyncLock myCollection.SyncRoot
    For Each item As Object In myCollection
        ' Insert your code here.
    Next item
End SyncLock

このプロパティの値の取得は @no__t 0 操作です。Retrieving the value of this property is an O(1) operation.

次のコード例では、ArrayList を同期し、@no__t が同期されているかどうかを判断し、同期された ArrayList を使用する方法を示します。The following code example shows how to synchronize an ArrayList, determine if an ArrayList is synchronized and use a synchronized ArrayList.

using namespace System;
using namespace System::Collections;
int main()
{
   
   // Creates and initializes a new ArrayList instance.
   ArrayList^ myAL = gcnew ArrayList;
   myAL->Add( "The" );
   myAL->Add( "quick" );
   myAL->Add( "brown" );
   myAL->Add( "fox" );
   
   // Creates a synchronized wrapper around the ArrayList.
   ArrayList^ mySyncdAL = ArrayList::Synchronized( myAL );
   
   // Displays the sychronization status of both ArrayLists.
   String^ szRes = myAL->IsSynchronized ?  (String^)"synchronized" :  "not synchronized";
   Console::WriteLine(  "myAL is {0}.", szRes );
   String^ szSyncRes = mySyncdAL->IsSynchronized ?  (String^)"synchronized" :  "not synchronized";
   Console::WriteLine(  "mySyncdAL is {0}.", szSyncRes );
}

/* 
 This code produces the following output.
 
 myAL is not synchronized.
 mySyncdAL is synchronized.
 */
using System;
using System.Collections;
public class SamplesArrayList  {

   public static void Main()  {

      // Creates and initializes a new ArrayList.
      ArrayList myAL = new ArrayList();
      myAL.Add( "The" );
      myAL.Add( "quick" );
      myAL.Add( "brown" );
      myAL.Add( "fox" );

      // Creates a synchronized wrapper around the ArrayList.
      ArrayList mySyncdAL = ArrayList.Synchronized( myAL );

      // Displays the sychronization status of both ArrayLists.
      Console.WriteLine( "myAL is {0}.", myAL.IsSynchronized ? "synchronized" : "not synchronized" );
      Console.WriteLine( "mySyncdAL is {0}.", mySyncdAL.IsSynchronized ? "synchronized" : "not synchronized" );
   }
}
/* 
This code produces the following output.

myAL is not synchronized.
mySyncdAL is synchronized.
*/ 
Imports System.Collections

Public Class SamplesArrayList
    
    
    Public Shared Sub Main()
        
        ' Creates and initializes a new ArrayList.
        Dim myAL As New ArrayList()
        myAL.Add("The")
        myAL.Add("quick")
        myAL.Add("brown")
        myAL.Add("fox")
        
        ' Creates a synchronized wrapper around the ArrayList.
        Dim mySyncdAL As ArrayList = ArrayList.Synchronized(myAL)
        
        ' Displays the sychronization status of both ArrayLists.
        Dim str As String
        If myAL.IsSynchronized Then
            str = "synchronized"
        Else
            str = "not synchronized"
        End If
        Console.WriteLine("myAL is {0}.", str)
        If mySyncdAL.IsSynchronized Then
            str = "synchronized"
        Else
            str = "not synchronized"
        End If
        Console.WriteLine("mySyncdAL is {0}.", str)
    End Sub
End Class

' This code produces the following output.
' 
' myAL is not synchronized.
' mySyncdAL is synchronized. 

注釈

@No__t 0 のスレッドセーフを保証するには、すべての操作を、Synchronized メソッドによって返されるラッパーを介して行う必要があります。To guarantee the thread safety of the ArrayList, all operations must be done through the wrapper returned by the Synchronized method.

コレクションの列挙は、本質的にスレッド セーフなプロシージャではありません。Enumerating through a collection is intrinsically not a thread-safe procedure. コレクションの同期がとられている場合でも、別のスレッドによってそのコレクションを変更できるため、変更の結果として列挙子は例外をスローします。Even when a collection is synchronized, other threads can still modify the collection, which causes the enumerator to throw an exception. 列挙処理を確実にスレッド セーフに行うには、列挙中にコレクションをロックするか、他のスレッドによって行われた変更によってスローされる例外をキャッチします。To guarantee thread safety during enumeration, you can either lock the collection during the entire enumeration or catch the exceptions resulting from changes made by other threads.

適用対象

こちらもご覧ください