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Stack.Pop Method

Removes and returns the object at the top of the Stack.

Namespace: System.Collections
Assembly: mscorlib (in mscorlib.dll)

public virtual Object Pop ()
public Object Pop ()
public function Pop () : Object
Not applicable.

Return Value

The Object removed from the top of the Stack.

Exception typeCondition

InvalidOperationException

The Stack is empty.

This method is similar to the Peek method, but Peek does not modify the Stack.

a null reference (Nothing in Visual Basic) can be pushed onto the Stack as a placeholder, if needed. To distinguish between a null value and the end of the stack, check the Count property or catch the InvalidOperationException, which is thrown when the Stack is empty.

Stack is implemented as a circular buffer. This method is an O(1) operation.

The following example shows how to add elements to the Stack, remove elements from the Stack, or view the element at the top of the Stack.

using System;
using System.Collections;
public class SamplesStack  {

   public static void Main()  {

      // Creates and initializes a new Stack.
      Stack myStack = new Stack();
      myStack.Push( "The" );
      myStack.Push( "quick" );
      myStack.Push( "brown" );
      myStack.Push( "fox" );

      // Displays the Stack.
      Console.Write( "Stack values:" );
      PrintValues( myStack, '\t' );

      // Removes an element from the Stack.
      Console.WriteLine( "(Pop)\t\t{0}", myStack.Pop() );

      // Displays the Stack.
      Console.Write( "Stack values:" );
      PrintValues( myStack, '\t' );

      // Removes another element from the Stack.
      Console.WriteLine( "(Pop)\t\t{0}", myStack.Pop() );

      // Displays the Stack.
      Console.Write( "Stack values:" );
      PrintValues( myStack, '\t' );

      // Views the first element in the Stack but does not remove it.
      Console.WriteLine( "(Peek)\t\t{0}", myStack.Peek() );

      // Displays the Stack.
      Console.Write( "Stack values:" );
      PrintValues( myStack, '\t' );
   }


   public static void PrintValues( IEnumerable myCollection, char mySeparator )  {
      foreach ( Object obj in myCollection )
         Console.Write( "{0}{1}", mySeparator, obj );
      Console.WriteLine();
   }

}


/* 
This code produces the following output.

Stack values:    fox    brown    quick    The
(Pop)        fox
Stack values:    brown    quick    The
(Pop)        brown
Stack values:    quick    The
(Peek)        quick
Stack values:    quick    The
*/ 


import System.*;
import System.Collections.*;

public class SamplesStack
{

    public static void main(String[] args)
    {
        // Creates and initializes a new Stack.
        Stack myStack = new Stack();

        myStack.Push("The");
        myStack.Push("quick");
        myStack.Push("brown");
        myStack.Push("fox");

        // Displays the Stack.
        Console.Write("Stack values:");
        PrintValues(myStack, '\t');

        // Removes an element from the Stack.
        Console.WriteLine("(Pop)\t\t{0}", myStack.Pop());

        // Displays the Stack.
        Console.Write("Stack values:");
        PrintValues(myStack, '\t');

        // Removes another element from the Stack.
        Console.WriteLine("(Pop)\t\t{0}", myStack.Pop());

        // Displays the Stack.
        Console.Write("Stack values:");
        PrintValues(myStack, '\t');

        // Views the first element in the Stack but does not remove it.
        Console.WriteLine("(Peek)\t\t{0}", myStack.Peek());

        // Displays the Stack.
        Console.Write("Stack values:");
        PrintValues(myStack, '\t');
    } //main

    public static void PrintValues(IEnumerable myCollection, char mySeparator)
    {
        IEnumerator l_objmyEnum = myCollection.GetEnumerator();
        while (l_objmyEnum.MoveNext()) {
            Console.Write("{0}{1}", 
                System.Convert.ToString(mySeparator), 
                System.Convert.ToString(l_objmyEnum.get_Current()));
        }
        Console.WriteLine();
    } //PrintValues

} //SamplesStack

/* 
 This code produces the following output.
 
Stack values:   fox     brown   quick   The
(Pop)           fox
Stack values:   brown   quick   The
(Pop)           brown
Stack values:   quick   The
(Peek)          quick
Stack values:   quick   The
 */

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

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