Stack<T>.Push(T) 方法

參考

定義

命名空間:: System.Collections.Generic

組件:: System.Collections.dll

組件:: System.dll

組件:: netstandard.dll

來源:: Stack.cs

來源:: Stack.cs

來源:: Stack.cs

重要

部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。

將物件插入 Stack<T> 的頂端。

public:
 void Push(T item);

public void Push (T item);

member this.Push : 'T -> unit

Public Sub Push (item As T)

參數

item: T

要推送至 Stack<T> 的物件。參考類型的值可以是 null。

範例

下列程式代碼範例示範泛型類別的 Stack<T> 數種方法，包括 Push 方法。

程式代碼範例會建立具有預設容量的字串堆疊，並使用 Push 方法將五個字元串推送至堆疊。會列舉堆疊的專案，而不會變更堆疊的狀態。方法 Pop 可用來從堆疊中快顯第一個字串。方法 Peek 可用來查看堆疊上的下一個專案，然後使用 Pop 方法將其快顯。

方法 ToArray 可用來建立陣列，並將堆疊元素複製到該陣列，然後將數位傳遞至 Stack<T> 採用 IEnumerable<T>的建構函式，並使用反轉元素的順序建立堆疊複本。複本的專案隨即顯示。

建立堆疊大小的兩次數組，而 CopyTo 方法會用來複製陣列元素，從陣列中間開始。建 Stack<T> 構函式會再次用來建立堆疊複本，並反轉元素的順序;因此，三個 Null 元素位於結尾。

方法 Contains 用來顯示字串「four」位在堆疊的第一個複本中，之後 Clear 方法會清除複本，而 Count 屬性會顯示堆疊是空的。

using System;
using System.Collections.Generic;

class Example
{
    public static void Main()
    {
        Stack<string> numbers = new Stack<string>();
        numbers.Push("one");
        numbers.Push("two");
        numbers.Push("three");
        numbers.Push("four");
        numbers.Push("five");

        // A stack can be enumerated without disturbing its contents.
        foreach( string number in numbers )
        {
            Console.WriteLine(number);
        }

        Console.WriteLine("\nPopping '{0}'", numbers.Pop());
        Console.WriteLine("Peek at next item to destack: {0}",
            numbers.Peek());
        Console.WriteLine("Popping '{0}'", numbers.Pop());

        // Create a copy of the stack, using the ToArray method and the
        // constructor that accepts an IEnumerable<T>.
        Stack<string> stack2 = new Stack<string>(numbers.ToArray());

        Console.WriteLine("\nContents of the first copy:");
        foreach( string number in stack2 )
        {
            Console.WriteLine(number);
        }

        // Create an array twice the size of the stack and copy the
        // elements of the stack, starting at the middle of the
        // array.
        string[] array2 = new string[numbers.Count * 2];
        numbers.CopyTo(array2, numbers.Count);

        // Create a second stack, using the constructor that accepts an
        // IEnumerable(Of T).
        Stack<string> stack3 = new Stack<string>(array2);

        Console.WriteLine("\nContents of the second copy, with duplicates and nulls:");
        foreach( string number in stack3 )
        {
            Console.WriteLine(number);
        }

        Console.WriteLine("\nstack2.Contains(\"four\") = {0}",
            stack2.Contains("four"));

        Console.WriteLine("\nstack2.Clear()");
        stack2.Clear();
        Console.WriteLine("\nstack2.Count = {0}", stack2.Count);
    }
}

/* This code example produces the following output:

five
four
three
two
one

Popping 'five'
Peek at next item to destack: four
Popping 'four'

Contents of the first copy:
one
two
three

Contents of the second copy, with duplicates and nulls:
one
two
three




stack2.Contains("four") = False

stack2.Clear()

stack2.Count = 0
 */

open System
open System.Collections.Generic

let numbers = Stack()
numbers.Push "one"
numbers.Push "two"
numbers.Push "three"
numbers.Push "four"
numbers.Push "five"

// A stack can be enumerated without disturbing its contents.
for number in numbers do
    printfn $"{number}"

printfn $"\nPopping '{numbers.Pop()}'"
printfn $"Peek at next item to destack: {numbers.Peek()}"
numbers.Peek() |> ignore
printfn $"Popping '{numbers.Pop()}'"

// Create a copy of the stack, using the ToArray method and the
// constructor that accepts an IEnumerable<T>.
let stack2 = numbers.ToArray() |> Stack

printfn "\nContents of the first copy:"

for number in stack2 do
    printfn $"{number}"

// Create an array twice the size of the stack and copy the
// elements of the stack, starting at the middle of the
// array.
let array2 = numbers.Count * 2 |> Array.zeroCreate
numbers.CopyTo(array2, numbers.Count)

// Create a second stack, using the constructor that accepts an
// IEnumerable(Of T).
let stack3 = Stack array2

printfn "\nContents of the second copy, with duplicates and nulls:"

for number in stack3 do
    printfn $"{number}"

printfn
    $"""
stack2.Contains "four" = {stack2.Contains "four"}"""

printfn "\nstack2.Clear()"
stack2.Clear()
printfn $"\nstack2.Count = {stack2.Count}"

// This code example produces the following output:
//       five
//       four
//       three
//       two
//       one
//
//       Popping 'five'
//       Peek at next item to destack: four
//       Popping 'four'
//
//       Contents of the first copy:
//       one
//       two
//       three
//
//       Contents of the second copy, with duplicates and nulls:
//       one
//       two
//       three
//
//       stack2.Contains("four") = False
//
//       stack2.Clear()
//
//       stack2.Count = 0

Imports System.Collections.Generic

Module Example

    Sub Main

        Dim numbers As New Stack(Of String)
        numbers.Push("one")
        numbers.Push("two")
        numbers.Push("three")
        numbers.Push("four")
        numbers.Push("five")

        ' A stack can be enumerated without disturbing its contents.
        For Each number As String In numbers
            Console.WriteLine(number)
        Next

        Console.WriteLine(vbLf & "Popping '{0}'", numbers.Pop())
        Console.WriteLine("Peek at next item to pop: {0}", _
            numbers.Peek())    
        Console.WriteLine("Popping '{0}'", numbers.Pop())

        ' Create another stack, using the ToArray method and the
        ' constructor that accepts an IEnumerable(Of T). Note that
        ' the order of items on the new stack is reversed.
        Dim stack2 As New Stack(Of String)(numbers.ToArray())

        Console.WriteLine(vbLf & "Contents of the first copy:")
        For Each number As String In stack2
            Console.WriteLine(number)
        Next
        
        ' Create an array twice the size of the stack, compensating
        ' for the fact that Visual Basic allocates an extra array 
        ' element. Copy the elements of the stack, starting at the
        ' middle of the array. 
        Dim array2((numbers.Count * 2) - 1) As String
        numbers.CopyTo(array2, numbers.Count)
        
        ' Create a second stack, using the constructor that accepts an
        ' IEnumerable(Of T). The elements are reversed, with the null
        ' elements appearing at the end of the stack when enumerated.
        Dim stack3 As New Stack(Of String)(array2)

        Console.WriteLine(vbLf & _
            "Contents of the second copy, with duplicates and nulls:")
        For Each number As String In stack3
            Console.WriteLine(number)
        Next

        Console.WriteLine(vbLf & "stack2.Contains(""four"") = {0}", _
            stack2.Contains("four"))

        Console.WriteLine(vbLf & "stack2.Clear()")
        stack2.Clear()
        Console.WriteLine(vbLf & "stack2.Count = {0}", _
            stack2.Count)
    End Sub
End Module

' This code example produces the following output:
'
'five
'four
'three
'two
'one
'
'Popping 'five'
'Peek at next item to pop: four
'Popping 'four'
'
'Contents of the first copy:
'one
'two
'three
'
'Contents of the second copy, with duplicates and nulls:
'one
'two
'three
'
'
'
'
'stack2.Contains("four") = False
'
'stack2.Clear()
'
'stack2.Count = 0

備註

Stack<T> 實作為陣列。

如果 Count 已經等於容量，則會藉由自動重新配置內部數位來增加的容量 Stack<T> ，並在新增專案之前，將現有的元素複製到新的陣列。

如果 type T 是參考型別， null 可以視需要推送至 Stack<T> 作為佔位符。它會佔用堆疊中的位置，並視為任何物件。

如果 Count 小於堆疊的容量， Push 則為 O (1) 作業。如果需要增加容量以容納新的元素， Push 就會變成 O (n) 作業，其中 n 是 Count。

適用於

另請參閱

Peek()
Pop()

共用方式為

Stack<T>.Push(T) 方法

定義

參數

範例

備註

適用於

另請參閱

其他資源