ArrayList.Clear Method
Removes all elements from the ArrayList.
[Visual Basic] Public Overridable Sub Clear() Implements IList.Clear [C#] public virtual void Clear(); [C++] public: virtual void Clear(); [JScript] public function Clear();
Implements
Exceptions
| Exception Type | Condition |
|---|---|
| NotSupportedException | The ArrayList is read-only.
-or- The ArrayList has a fixed size. |
Remarks
Count is set to zero. Capacity remains unchanged. To reset the capacity of the ArrayList, call TrimToSize or set the Capacity property directly. Trimming an empty ArrayList sets the capacity of the ArrayList to the default capacity, not zero.
Example
The following example shows how to trim the unused portions of the ArrayList and how to clear the values of the ArrayList.
[Visual Basic] Imports System Imports System.Collections Imports Microsoft.VisualBasic 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") myAL.Add("jumped") ' Displays the count, capacity and values of the ArrayList. Console.WriteLine("Initially,") Console.WriteLine(" Count : {0}", myAL.Count) Console.WriteLine(" Capacity : {0}", myAL.Capacity) Console.Write(" Values:") PrintValues(myAL) ' Trim the ArrayList. myAL.TrimToSize() ' Displays the count, capacity and values of the ArrayList. Console.WriteLine("After TrimToSize,") Console.WriteLine(" Count : {0}", myAL.Count) Console.WriteLine(" Capacity : {0}", myAL.Capacity) Console.Write(" Values:") PrintValues(myAL) ' Clear the ArrayList. myAL.Clear() ' Displays the count, capacity and values of the ArrayList. Console.WriteLine("After Clear,") Console.WriteLine(" Count : {0}", myAL.Count) Console.WriteLine(" Capacity : {0}", myAL.Capacity) Console.Write(" Values:") PrintValues(myAL) ' Trim the ArrayList again. myAL.TrimToSize() ' Displays the count, capacity and values of the ArrayList. Console.WriteLine("After the second TrimToSize,") Console.WriteLine(" Count : {0}", myAL.Count) Console.WriteLine(" Capacity : {0}", myAL.Capacity) Console.Write(" Values:") PrintValues(myAL) End Sub Public Shared Sub PrintValues(myList As IEnumerable) Dim myEnumerator As System.Collections.IEnumerator = _ myList.GetEnumerator() While myEnumerator.MoveNext() Console.Write(ControlChars.Tab + "{0}", myEnumerator.Current) End While Console.WriteLine() End Sub End Class ' This code produces the following output. ' ' Initially, ' Count : 5 ' Capacity : 16 ' Values: The quick brown fox jumped ' After TrimToSize, ' Count : 5 ' Capacity : 5 ' Values: The quick brown fox jumped ' After Clear, ' Count : 0 ' Capacity : 5 ' Values: ' After the second TrimToSize, ' Count : 0 ' Capacity : 16 ' Values: [C#] 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" ); myAL.Add( "jumped" ); // Displays the count, capacity and values of the ArrayList. Console.WriteLine( "Initially," ); Console.WriteLine( " Count : {0}", myAL.Count ); Console.WriteLine( " Capacity : {0}", myAL.Capacity ); Console.Write( " Values:" ); PrintValues( myAL ); // Trim the ArrayList. myAL.TrimToSize(); // Displays the count, capacity and values of the ArrayList. Console.WriteLine( "After TrimToSize," ); Console.WriteLine( " Count : {0}", myAL.Count ); Console.WriteLine( " Capacity : {0}", myAL.Capacity ); Console.Write( " Values:" ); PrintValues( myAL ); // Clear the ArrayList. myAL.Clear(); // Displays the count, capacity and values of the ArrayList. Console.WriteLine( "After Clear," ); Console.WriteLine( " Count : {0}", myAL.Count ); Console.WriteLine( " Capacity : {0}", myAL.Capacity ); Console.Write( " Values:" ); PrintValues( myAL ); // Trim the ArrayList again. myAL.TrimToSize(); // Displays the count, capacity and values of the ArrayList. Console.WriteLine( "After the second TrimToSize," ); Console.WriteLine( " Count : {0}", myAL.Count ); Console.WriteLine( " Capacity : {0}", myAL.Capacity ); Console.Write( " Values:" ); PrintValues( myAL ); } public static void PrintValues( IEnumerable myList ) { System.Collections.IEnumerator myEnumerator = myList.GetEnumerator(); while ( myEnumerator.MoveNext() ) Console.Write( "\t{0}", myEnumerator.Current ); Console.WriteLine(); } } /* This code produces the following output. Initially, Count : 5 Capacity : 16 Values: The quick brown fox jumped After TrimToSize, Count : 5 Capacity : 5 Values: The quick brown fox jumped After Clear, Count : 0 Capacity : 5 Values: After the second TrimToSize, Count : 0 Capacity : 16 Values: */ [C++] #using <mscorlib.dll> using namespace System; using namespace System::Collections; void PrintValues( IEnumerable* myList ); void main() { // Creates and initializes a new ArrayList. ArrayList* myAL = new ArrayList(); myAL->Add( S"The" ); myAL->Add( S"quick" ); myAL->Add( S"brown" ); myAL->Add( S"fox" ); myAL->Add( S"jumped" ); // Displays the count, capacity and values of the ArrayList. Console::WriteLine( "Initially," ); Console::WriteLine( " Count : {0}", __box(myAL->Count) ); Console::WriteLine( " Capacity : {0}", __box(myAL->Capacity) ); Console::Write( " Values:" ); PrintValues( myAL ); // Trims the ArrayList. myAL->TrimToSize(); // Displays the count, capacity and values of the ArrayList. Console::WriteLine( "After TrimToSize," ); Console::WriteLine( " Count : {0}", __box(myAL->Count) ); Console::WriteLine( " Capacity : {0}", __box(myAL->Capacity) ); Console::Write( " Values:" ); PrintValues( myAL ); // Clears the ArrayList. myAL->Clear(); // Displays the count, capacity and values of the ArrayList. Console::WriteLine( "After Clear," ); Console::WriteLine( " Count : {0}", __box(myAL->Count) ); Console::WriteLine( " Capacity : {0}", __box(myAL->Capacity) ); Console::Write( " Values:" ); PrintValues( myAL ); // Trims the ArrayList again. myAL->TrimToSize(); // Displays the count, capacity and values of the ArrayList. Console::WriteLine( "After the second TrimToSize," ); Console::WriteLine( " Count : {0}", __box(myAL->Count) ); Console::WriteLine( " Capacity : {0}", __box(myAL->Capacity) ); Console::Write( " Values:" ); PrintValues( myAL ); } void PrintValues( IEnumerable* myList ) { System::Collections::IEnumerator* myEnumerator = myList->GetEnumerator(); while ( myEnumerator->MoveNext() ) Console::Write( "\t{0}", myEnumerator->Current ); Console::WriteLine(); } /* This code produces the following output. Initially, Count : 5 Capacity : 16 Values: The quick brown fox jumped After TrimToSize, Count : 5 Capacity : 5 Values: The quick brown fox jumped After Clear, Count : 0 Capacity : 5 Values: After the second TrimToSize, Count : 0 Capacity : 16 Values: */ [JScript] import System; import System.Collections; // Creates and initializes a new ArrayList. var myAL : ArrayList = new ArrayList(); myAL.Add( "The" ); myAL.Add( "quick" ); myAL.Add( "brown" ); myAL.Add( "fox" ); myAL.Add( "jumped" ); // Displays the count, capacity and values of the ArrayList. Console.WriteLine( "Initially," ); Console.WriteLine( " Count : {0}", myAL.Count ); Console.WriteLine( " Capacity : {0}", myAL.Capacity ); Console.Write( " Values:" ); PrintValues( myAL ); // Trim the ArrayList. myAL.TrimToSize(); // Displays the count, capacity and values of the ArrayList. Console.WriteLine( "After TrimToSize," ); Console.WriteLine( " Count : {0}", myAL.Count ); Console.WriteLine( " Capacity : {0}", myAL.Capacity ); Console.Write( " Values:" ); PrintValues( myAL ); // Clear the ArrayList. myAL.Clear(); // Displays the count, capacity and values of the ArrayList. Console.WriteLine( "After Clear," ); Console.WriteLine( " Count : {0}", myAL.Count ); Console.WriteLine( " Capacity : {0}", myAL.Capacity ); Console.Write( " Values:" ); PrintValues( myAL ); // Trim the ArrayList again. myAL.TrimToSize(); // Displays the count, capacity and values of the ArrayList. Console.WriteLine( "After the second TrimToSize," ); Console.WriteLine( " Count : {0}", myAL.Count ); Console.WriteLine( " Capacity : {0}", myAL.Capacity ); Console.Write( " Values:" ); PrintValues( myAL ); function PrintValues( myList : IEnumerable) { var myEnumerator : System.Collections.IEnumerator = myList.GetEnumerator(); while ( myEnumerator.MoveNext() ) Console.Write( "\t{0}", myEnumerator.Current ); Console.WriteLine(); } /* This code produces the following output. Initially, Count : 5 Capacity : 16 Values: The quick brown fox jumped After TrimToSize, Count : 5 Capacity : 5 Values: The quick brown fox jumped After Clear, Count : 0 Capacity : 5 Values: After the second TrimToSize, Count : 0 Capacity : 16 Values: */
Requirements
Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework, Common Language Infrastructure (CLI) Standard
See Also
ArrayList Class | ArrayList Members | System.Collections Namespace | TrimToSize | Capacity | Count