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C# Queue.Peek用法及代碼示例


此方法在不刪除隊列的情況下返回該對象。此方法類似於出隊方法，但是Peek不會修改Queue，並且是O(1)操作。此方法位於System.Collections命名空間下。

用法:

public virtual object Peek ();

返回值：隊列開始處的對象。


異常：如果Queue為空，則此方法將提供InvalidOperationException。

以下示例程序旨在說明上述方法的使用：

示例1:

// C# code to illustrate the 
// Queue.Peek Method 
using System; 
using System.Collections; 
  
class GFG { 
  
    // Driver code 
    public static void Main() 
    { 
  
        // Creating a Queue 
        Queue myQueue = new Queue(); 
  
        // Inserting the elements into the Queue 
        myQueue.Enqueue("1st Element"); 
        myQueue.Enqueue("2nd Element"); 
        myQueue.Enqueue("3rd Element"); 
        myQueue.Enqueue("4th Element"); 
        myQueue.Enqueue("5th Element"); 
        myQueue.Enqueue("6th Element"); 
  
        // Displaying the count of elements 
        // contained in the Queue 
        Console.Write("Total number of elements in the Queue are : "); 
  
        Console.WriteLine(myQueue.Count); 
  
        // Displaying the beginning element of Queue 
        // without removing it from the Queue 
        Console.WriteLine("Element at the beginning is : " 
                                        + myQueue.Peek()); 
  
        // Displaying the beginning element of Queue 
        // without removing it from the Queue 
        Console.WriteLine("Element at the beginning is : " 
                                        + myQueue.Peek()); 
  
        // Displaying the count of elements 
        // contained in the Queue 
        Console.Write("Total number of elements in the Queue are : "); 
  
        Console.WriteLine(myQueue.Count); 
    } 
}

輸出：

Total number of elements in the Queue are : 6
Element at the beginning is : 1st Element
Element at the beginning is : 1st Element
Total number of elements in the Queue are : 6

示例2:

// C# code to illustrate the 
// Queue.Peek Method 
using System; 
using System.Collections; 
  
class GFG { 
  
    // Driver code 
    public static void Main() 
    { 
  
        // Creating a Queue 
        Queue myQueue = new Queue(); 
  
        // Displaying the beginning element of Queue 
        // without removing it from the Queue 
        // Calling Peek() method on empty Queue 
        // will throw InvalidOperationException. 
        Console.WriteLine("Element at the beginning is : "
                                       + myQueue.Peek()); 
    } 
}

運行時錯誤：

Unhandled Exception:
System.InvalidOperationException: Queue empty.

參考：



相關用法


注：本文由純淨天空篩選整理自Kirti_Mangal大神的英文原創作品 Queue.Peek Method in C#。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。