DictionaryBase.IDictionary.Add(Object, Object) 方法

定義

將有指定索引鍵和數值的項目加入 DictionaryBaseAdds an element with the specified key and value into the DictionaryBase.

 virtual void System.Collections.IDictionary.Add(System::Object ^ key, System::Object ^ value) = System::Collections::IDictionary::Add;
void IDictionary.Add (object key, object value);
abstract member System.Collections.IDictionary.Add : obj * obj -> unit
override this.System.Collections.IDictionary.Add : obj * obj -> unit
Sub Add (key As Object, value As Object) Implements IDictionary.Add

參數

key
Object

要加入的項目的索引鍵。The key of the element to add.

value
Object

要加入的項目的值。The value of the element to add.

實作

例外狀況

keynullkey is null.

DictionaryBase 中已存在具有相同索引鍵的元素。An element with the same key already exists in the DictionaryBase.

DictionaryBase 為唯讀。The DictionaryBase is read-only.

-或--or- DictionaryBase 具有固定的大小。The DictionaryBase has a fixed size.

範例

下列程式碼範例會 DictionaryBase 實作為類別,並使用該執行來建立索引 String 鍵的字典以及 Length 5 個字元以下的值。The following code example implements the DictionaryBase class and uses that implementation to create a dictionary of String keys and values that have a Length of 5 characters or less.

using namespace System;
using namespace System::Collections;

public ref class ShortStringDictionary: public DictionaryBase
{
public:

   property String^ Item [String^]
   {
      String^ get( String^ key )
      {
         return (dynamic_cast<String^>(Dictionary[ key ]));
      }

      void set( String^ value, String^ key )
      {
         Dictionary[ key ] = value;
      }
   }

   property ICollection^ Keys 
   {
      ICollection^ get()
      {
         return (Dictionary->Keys);
      }
   }

   property ICollection^ Values 
   {
      ICollection^ get()
      {
         return (Dictionary->Values);
      }
   }
   void Add( String^ key, String^ value )
   {
      Dictionary->Add( key, value );
   }

   bool Contains( String^ key )
   {
      return (Dictionary->Contains( key ));
   }

   void Remove( String^ key )
   {
      Dictionary->Remove( key );
   }


protected:
   virtual void OnInsert( Object^ key, Object^ value ) override
   {
      if ( key->GetType() != Type::GetType( "System.String" ) )
            throw gcnew ArgumentException( "key must be of type String.","key" );
      else
      {
         String^ strKey = dynamic_cast<String^>(key);
         if ( strKey->Length > 5 )
                  throw gcnew ArgumentException( "key must be no more than 5 characters in length.","key" );
      }

      if ( value->GetType() != Type::GetType( "System.String" ) )
            throw gcnew ArgumentException( "value must be of type String.","value" );
      else
      {
         String^ strValue = dynamic_cast<String^>(value);
         if ( strValue->Length > 5 )
                  throw gcnew ArgumentException( "value must be no more than 5 characters in length.","value" );
      }
   }

   virtual void OnRemove( Object^ key, Object^ /*value*/ ) override
   {
      if ( key->GetType() != Type::GetType( "System.String" ) )
            throw gcnew ArgumentException( "key must be of type String.","key" );
      else
      {
         String^ strKey = dynamic_cast<String^>(key);
         if ( strKey->Length > 5 )
                  throw gcnew ArgumentException( "key must be no more than 5 characters in length.","key" );
      }
   }

   virtual void OnSet( Object^ key, Object^ /*oldValue*/, Object^ newValue ) override
   {
      if ( key->GetType() != Type::GetType( "System.String" ) )
            throw gcnew ArgumentException( "key must be of type String.","key" );
      else
      {
         String^ strKey = dynamic_cast<String^>(key);
         if ( strKey->Length > 5 )
                  throw gcnew ArgumentException( "key must be no more than 5 characters in length.","key" );
      }

      if ( newValue->GetType() != Type::GetType( "System.String" ) )
            throw gcnew ArgumentException( "newValue must be of type String.","newValue" );
      else
      {
         String^ strValue = dynamic_cast<String^>(newValue);
         if ( strValue->Length > 5 )
                  throw gcnew ArgumentException( "newValue must be no more than 5 characters in length.","newValue" );
      }
   }

   virtual void OnValidate( Object^ key, Object^ value ) override
   {
      if ( key->GetType() != Type::GetType( "System.String" ) )
            throw gcnew ArgumentException( "key must be of type String.","key" );
      else
      {
         String^ strKey = dynamic_cast<String^>(key);
         if ( strKey->Length > 5 )
                  throw gcnew ArgumentException( "key must be no more than 5 characters in length.","key" );
      }

      if ( value->GetType() != Type::GetType( "System.String" ) )
            throw gcnew ArgumentException( "value must be of type String.","value" );
      else
      {
         String^ strValue = dynamic_cast<String^>(value);
         if ( strValue->Length > 5 )
                  throw gcnew ArgumentException( "value must be no more than 5 characters in length.","value" );
      }
   }

};

void PrintKeysAndValues2( ShortStringDictionary^ myCol );
void PrintKeysAndValues3( ShortStringDictionary^ myCol );
int main()
{
   // Creates and initializes a new DictionaryBase.
   ShortStringDictionary^ mySSC = gcnew ShortStringDictionary;

   // Adds elements to the collection.
   mySSC->Add( "One", "a" );
   mySSC->Add( "Two", "ab" );
   mySSC->Add( "Three", "abc" );
   mySSC->Add( "Four", "abcd" );
   mySSC->Add( "Five", "abcde" );

   // Display the contents of the collection using the enumerator.
   Console::WriteLine( "Contents of the collection (using enumerator):" );
   PrintKeysAndValues2( mySSC );

   // Display the contents of the collection using the Keys property and the Item property.
   Console::WriteLine( "Initial contents of the collection (using Keys and Item):" );
   PrintKeysAndValues3( mySSC );

   // Tries to add a value that is too long.
   try
   {
      mySSC->Add( "Ten", "abcdefghij" );
   }
   catch ( ArgumentException^ e ) 
   {
      Console::WriteLine( e );
   }

   // Tries to add a key that is too long.
   try
   {
      mySSC->Add( "Eleven", "ijk" );
   }
   catch ( ArgumentException^ e ) 
   {
      Console::WriteLine( e );
   }

   Console::WriteLine();

   // Searches the collection with Contains.
   Console::WriteLine( "Contains \"Three\": {0}", mySSC->Contains( "Three" ) );
   Console::WriteLine( "Contains \"Twelve\": {0}", mySSC->Contains( "Twelve" ) );
   Console::WriteLine();

   // Removes an element from the collection.
   mySSC->Remove( "Two" );

   // Displays the contents of the collection.
   Console::WriteLine( "After removing \"Two\":" );
   PrintKeysAndValues2( mySSC );
}

// Uses the enumerator. 
void PrintKeysAndValues2( ShortStringDictionary^ myCol )
{
   DictionaryEntry myDE;
   System::Collections::IEnumerator^ myEnumerator = myCol->GetEnumerator();
   while ( myEnumerator->MoveNext() )
      if ( myEnumerator->Current != nullptr )
   {
      myDE =  *dynamic_cast<DictionaryEntry^>(myEnumerator->Current);
      Console::WriteLine( "   {0,-5} : {1}", myDE.Key, myDE.Value );
   }

   Console::WriteLine();
}


// Uses the Keys property and the Item property.
void PrintKeysAndValues3( ShortStringDictionary^ myCol )
{
   ICollection^ myKeys = myCol->Keys;
   IEnumerator^ myEnum1 = myKeys->GetEnumerator();
   while ( myEnum1->MoveNext() )
   {
      String^ k = safe_cast<String^>(myEnum1->Current);
      Console::WriteLine( "   {0,-5} : {1}", k, myCol->Item[ k ] );
   }

   Console::WriteLine();
}

/* 
This code produces the following output.

Contents of the collection (using enumerator):
   Three : abc
   Five  : abcde
   Two   : ab
   One   : a
   Four  : abcd

Initial contents of the collection (using Keys and Item):
   Three : abc
   Five  : abcde
   Two   : ab
   One   : a
   Four  : abcd

System.ArgumentException: value must be no more than 5 characters in length.
Parameter name: value
   at ShortStringDictionary.OnValidate(Object key, Object value)
   at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
   at SamplesDictionaryBase.Main()
System.ArgumentException: key must be no more than 5 characters in length.
Parameter name: key
   at ShortStringDictionary.OnValidate(Object key, Object value)
   at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
   at SamplesDictionaryBase.Main()

Contains "Three": True
Contains "Twelve": False

After removing "Two":
   Three : abc
   Five  : abcde
   One   : a
   Four  : abcd

*/
using System;
using System.Collections;

public class ShortStringDictionary : DictionaryBase  {

   public String this[ String key ]  {
      get  {
         return( (String) Dictionary[key] );
      }
      set  {
         Dictionary[key] = value;
      }
   }

   public ICollection Keys  {
      get  {
         return( Dictionary.Keys );
      }
   }

   public ICollection Values  {
      get  {
         return( Dictionary.Values );
      }
   }

   public void Add( String key, String value )  {
      Dictionary.Add( key, value );
   }

   public bool Contains( String key )  {
      return( Dictionary.Contains( key ) );
   }

   public void Remove( String key )  {
      Dictionary.Remove( key );
   }

   protected override void OnInsert( Object key, Object value )  {
      if ( key.GetType() != typeof(System.String) )
        {
            throw new ArgumentException( "key must be of type String.", "key" );
        }
        else  {
         String strKey = (String) key;
         if ( strKey.Length > 5 )
            throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
      }

      if ( value.GetType() != typeof(System.String) )
        {
            throw new ArgumentException( "value must be of type String.", "value" );
        }
        else  {
         String strValue = (String) value;
         if ( strValue.Length > 5 )
            throw new ArgumentException( "value must be no more than 5 characters in length.", "value" );
      }
   }

   protected override void OnRemove( Object key, Object value )  {
      if ( key.GetType() != typeof(System.String) )
        {
            throw new ArgumentException( "key must be of type String.", "key" );
        }
        else  {
         String strKey = (String) key;
         if ( strKey.Length > 5 )
            throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
      }
   }

   protected override void OnSet( Object key, Object oldValue, Object newValue )  {
      if ( key.GetType() != typeof(System.String) )
        {
            throw new ArgumentException( "key must be of type String.", "key" );
        }
        else  {
         String strKey = (String) key;
         if ( strKey.Length > 5 )
            throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
      }

      if ( newValue.GetType() != typeof(System.String) )
        {
            throw new ArgumentException( "newValue must be of type String.", "newValue" );
        }
        else  {
         String strValue = (String) newValue;
         if ( strValue.Length > 5 )
            throw new ArgumentException( "newValue must be no more than 5 characters in length.", "newValue" );
      }
   }

   protected override void OnValidate( Object key, Object value )  {
      if ( key.GetType() != typeof(System.String) )
        {
            throw new ArgumentException( "key must be of type String.", "key" );
        }
        else  {
         String strKey = (String) key;
         if ( strKey.Length > 5 )
            throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
      }

      if ( value.GetType() != typeof(System.String) )
        {
            throw new ArgumentException( "value must be of type String.", "value" );
        }
        else  {
         String strValue = (String) value;
         if ( strValue.Length > 5 )
            throw new ArgumentException( "value must be no more than 5 characters in length.", "value" );
      }
   }
}

public class SamplesDictionaryBase  {

   public static void Main()  {

      // Creates and initializes a new DictionaryBase.
      ShortStringDictionary mySSC = new ShortStringDictionary();

      // Adds elements to the collection.
      mySSC.Add( "One", "a" );
      mySSC.Add( "Two", "ab" );
      mySSC.Add( "Three", "abc" );
      mySSC.Add( "Four", "abcd" );
      mySSC.Add( "Five", "abcde" );

      // Display the contents of the collection using foreach. This is the preferred method.
      Console.WriteLine( "Contents of the collection (using foreach):" );
      PrintKeysAndValues1( mySSC );

      // Display the contents of the collection using the enumerator.
      Console.WriteLine( "Contents of the collection (using enumerator):" );
      PrintKeysAndValues2( mySSC );

      // Display the contents of the collection using the Keys property and the Item property.
      Console.WriteLine( "Initial contents of the collection (using Keys and Item):" );
      PrintKeysAndValues3( mySSC );

      // Tries to add a value that is too long.
      try  {
         mySSC.Add( "Ten", "abcdefghij" );
      }
      catch ( ArgumentException e )  {
         Console.WriteLine( e.ToString() );
      }

      // Tries to add a key that is too long.
      try  {
         mySSC.Add( "Eleven", "ijk" );
      }
      catch ( ArgumentException e )  {
         Console.WriteLine( e.ToString() );
      }

      Console.WriteLine();

      // Searches the collection with Contains.
      Console.WriteLine( "Contains \"Three\": {0}", mySSC.Contains( "Three" ) );
      Console.WriteLine( "Contains \"Twelve\": {0}", mySSC.Contains( "Twelve" ) );
      Console.WriteLine();

      // Removes an element from the collection.
      mySSC.Remove( "Two" );

      // Displays the contents of the collection.
      Console.WriteLine( "After removing \"Two\":" );
      PrintKeysAndValues1( mySSC );
   }

   // Uses the foreach statement which hides the complexity of the enumerator.
   // NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
   public static void PrintKeysAndValues1( ShortStringDictionary myCol )  {
      foreach ( DictionaryEntry myDE in myCol )
         Console.WriteLine( "   {0,-5} : {1}", myDE.Key, myDE.Value );
      Console.WriteLine();
   }

   // Uses the enumerator.
   // NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
   public static void PrintKeysAndValues2( ShortStringDictionary myCol )  {
      DictionaryEntry myDE;
      System.Collections.IEnumerator myEnumerator = myCol.GetEnumerator();
      while ( myEnumerator.MoveNext() )
         if ( myEnumerator.Current != null )  {
            myDE = (DictionaryEntry) myEnumerator.Current;
            Console.WriteLine( "   {0,-5} : {1}", myDE.Key, myDE.Value );
         }
      Console.WriteLine();
   }

   // Uses the Keys property and the Item property.
   public static void PrintKeysAndValues3( ShortStringDictionary myCol )  {
      ICollection myKeys = myCol.Keys;
      foreach ( String k in myKeys )
         Console.WriteLine( "   {0,-5} : {1}", k, myCol[k] );
      Console.WriteLine();
   }
}


/*
This code produces the following output.

Contents of the collection (using foreach):
   Three : abc
   Five  : abcde
   Two   : ab
   One   : a
   Four  : abcd

Contents of the collection (using enumerator):
   Three : abc
   Five  : abcde
   Two   : ab
   One   : a
   Four  : abcd

Initial contents of the collection (using Keys and Item):
   Three : abc
   Five  : abcde
   Two   : ab
   One   : a
   Four  : abcd

System.ArgumentException: value must be no more than 5 characters in length.
Parameter name: value
   at ShortStringDictionary.OnValidate(Object key, Object value)
   at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
   at SamplesDictionaryBase.Main()
System.ArgumentException: key must be no more than 5 characters in length.
Parameter name: key
   at ShortStringDictionary.OnValidate(Object key, Object value)
   at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
   at SamplesDictionaryBase.Main()

Contains "Three": True
Contains "Twelve": False

After removing "Two":
   Three : abc
   Five  : abcde
   One   : a
   Four  : abcd

*/

Imports System.Collections

Public Class ShortStringDictionary
   Inherits DictionaryBase

   Default Public Property Item(key As String) As String
      Get
         Return CType(Dictionary(key), String)
      End Get
      Set
         Dictionary(key) = value
      End Set
   End Property

   Public ReadOnly Property Keys() As ICollection
      Get
         Return Dictionary.Keys
      End Get
   End Property

   Public ReadOnly Property Values() As ICollection
      Get
         Return Dictionary.Values
      End Get
   End Property

   Public Sub Add(key As String, value As String)
      Dictionary.Add(key, value)
   End Sub

   Public Function Contains(key As String) As Boolean
      Return Dictionary.Contains(key)
   End Function 'Contains

   Public Sub Remove(key As String)
      Dictionary.Remove(key)
   End Sub

   Protected Overrides Sub OnInsert(key As Object, value As Object)
      If Not GetType(System.String).IsAssignableFrom(key.GetType()) Then
         Throw New ArgumentException("key must be of type String.", "key")
      Else
         Dim strKey As String = CType(key, String)
         If strKey.Length > 5 Then
            Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
         End If
      End If 
      If Not GetType(System.String).IsAssignableFrom(value.GetType()) Then
         Throw New ArgumentException("value must be of type String.", "value")
      Else
         Dim strValue As String = CType(value, String)
         If strValue.Length > 5 Then
            Throw New ArgumentException("value must be no more than 5 characters in length.", "value")
         End If
      End If
   End Sub

   Protected Overrides Sub OnRemove(key As Object, value As Object)
      If Not GetType(System.String).IsAssignableFrom(key.GetType()) Then
         Throw New ArgumentException("key must be of type String.", "key")
      Else
         Dim strKey As String = CType(key, String)
         If strKey.Length > 5 Then
            Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
         End If
      End If
   End Sub

   Protected Overrides Sub OnSet(key As Object, oldValue As Object, newValue As Object)
      If Not GetType(System.String).IsAssignableFrom(key.GetType()) Then
         Throw New ArgumentException("key must be of type String.", "key")
      Else
         Dim strKey As String = CType(key, String)
         If strKey.Length > 5 Then
            Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
         End If
      End If 
      If Not GetType(System.String).IsAssignableFrom(newValue.GetType()) Then
         Throw New ArgumentException("newValue must be of type String.", "newValue")
      Else
         Dim strValue As String = CType(newValue, String)
         If strValue.Length > 5 Then
            Throw New ArgumentException("newValue must be no more than 5 characters in length.", "newValue")
         End If
      End If
   End Sub

   Protected Overrides Sub OnValidate(key As Object, value As Object)
      If Not GetType(System.String).IsAssignableFrom(key.GetType()) Then
         Throw New ArgumentException("key must be of type String.", "key")
      Else
         Dim strKey As String = CType(key, String)
         If strKey.Length > 5 Then
            Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
         End If
      End If 
      If Not GetType(System.String).IsAssignableFrom(value.GetType()) Then
         Throw New ArgumentException("value must be of type String.", "value")
      Else
         Dim strValue As String = CType(value, String)
         If strValue.Length > 5 Then
            Throw New ArgumentException("value must be no more than 5 characters in length.", "value")
         End If
      End If
   End Sub

End Class


Public Class SamplesDictionaryBase

   Public Shared Sub Main()

      ' Creates and initializes a new DictionaryBase.
      Dim mySSC As New ShortStringDictionary()

      ' Adds elements to the collection.
      mySSC.Add("One", "a")
      mySSC.Add("Two", "ab")
      mySSC.Add("Three", "abc")
      mySSC.Add("Four", "abcd")
      mySSC.Add("Five", "abcde")

      ' Display the contents of the collection using For Each. This is the preferred method.
      Console.WriteLine("Contents of the collection (using For Each):")
      PrintKeysAndValues1(mySSC)

      ' Display the contents of the collection using the enumerator.
      Console.WriteLine("Contents of the collection (using enumerator):")
      PrintKeysAndValues2(mySSC)

      ' Display the contents of the collection using the Keys property and the Item property.
      Console.WriteLine("Initial contents of the collection (using Keys and Item):")
      PrintKeysAndValues3(mySSC)

      ' Tries to add a value that is too long.
      Try
          mySSC.Add("Ten", "abcdefghij")
      Catch e As ArgumentException
          Console.WriteLine(e.ToString())
      End Try

      ' Tries to add a key that is too long.
      Try
          mySSC.Add("Eleven", "ijk")
      Catch e As ArgumentException
          Console.WriteLine(e.ToString())
      End Try

      Console.WriteLine()

      ' Searches the collection with Contains.
      Console.WriteLine("Contains ""Three"": {0}", mySSC.Contains("Three"))
      Console.WriteLine("Contains ""Twelve"": {0}", mySSC.Contains("Twelve"))
      Console.WriteLine()

      ' Removes an element from the collection.
      mySSC.Remove("Two")

      ' Displays the contents of the collection.
      Console.WriteLine("After removing ""Two"":")
      PrintKeysAndValues1(mySSC)

    End Sub


    ' Uses the For Each statement which hides the complexity of the enumerator.
    ' NOTE: The For Each statement is the preferred way of enumerating the contents of a collection.
    Public Shared Sub PrintKeysAndValues1(myCol As ShortStringDictionary)
      Dim myDE As DictionaryEntry
      For Each myDE In  myCol
          Console.WriteLine("   {0,-5} : {1}", myDE.Key, myDE.Value)
      Next myDE
      Console.WriteLine()
    End Sub


    ' Uses the enumerator. 
    ' NOTE: The For Each statement is the preferred way of enumerating the contents of a collection.
    Public Shared Sub PrintKeysAndValues2(myCol As ShortStringDictionary)
      Dim myDE As DictionaryEntry
      Dim myEnumerator As System.Collections.IEnumerator = myCol.GetEnumerator()
      While myEnumerator.MoveNext()
          If Not (myEnumerator.Current Is Nothing) Then
            myDE = CType(myEnumerator.Current, DictionaryEntry)
            Console.WriteLine("   {0,-5} : {1}", myDE.Key, myDE.Value)
          End If
      End While
      Console.WriteLine()
    End Sub


    ' Uses the Keys property and the Item property.
    Public Shared Sub PrintKeysAndValues3(myCol As ShortStringDictionary)
      Dim myKeys As ICollection = myCol.Keys
      Dim k As String
      For Each k In  myKeys
          Console.WriteLine("   {0,-5} : {1}", k, myCol(k))
      Next k
      Console.WriteLine()
    End Sub

End Class


'This code produces the following output.
'
'Contents of the collection (using For Each):
'   Three : abc
'   Five  : abcde
'   Two   : ab
'   One   : a
'   Four  : abcd
'
'Contents of the collection (using enumerator):
'   Three : abc
'   Five  : abcde
'   Two   : ab
'   One   : a
'   Four  : abcd
'
'Initial contents of the collection (using Keys and Item):
'   Three : abc
'   Five  : abcde
'   Two   : ab
'   One   : a
'   Four  : abcd
'
'System.ArgumentException: value must be no more than 5 characters in length.
'Parameter name: value
'   at ShortStringDictionary.OnValidate(Object key, Object value)
'   at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
'   at SamplesDictionaryBase.Main()
'System.ArgumentException: key must be no more than 5 characters in length.
'Parameter name: key
'   at ShortStringDictionary.OnValidate(Object key, Object value)
'   at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
'   at SamplesDictionaryBase.Main()
'
'Contains "Three": True
'Contains "Twelve": False
'
'After removing "Two":
'   Three : abc
'   Five  : abcde
'   One   : a
'   Four  : abcd

備註

在其狀態與其雜湊碼值之間沒有相互關聯的物件通常不應該當做索引鍵使用。An object that has no correlation between its state and its hash code value should typically not be used as the key. 例如, String 物件優於 StringBuilder 作為索引鍵使用的物件。For example, String objects are better than StringBuilder objects for use as keys.

您也可以使用 Item[] 屬性來加入新的專案,方法是設定不存在於中的索引鍵值 DictionaryBase ; 例如 myCollection["myNonexistentKey"] = myValueYou can also use the Item[] property to add new elements by setting the value of a key that does not exist in the DictionaryBase; for example, myCollection["myNonexistentKey"] = myValue. 但是,如果指定的索引鍵已經存在於中 DictionaryBase ,則設定 Item[] 屬性會覆寫舊的值。However, if the specified key already exists in the DictionaryBase, setting the Item[] property overwrites the old value. 相反地,此 Add 方法不會修改現有的元素。In contrast, the Add method does not modify existing elements.

這個方法是一項作業 O(1)This method is an O(1) operation.

適用於

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