C# Queue.Peek用法及代码示例

此方法在不删除队列的情况下返回该对象。此方法类似于出队方法，但是Peek不会修改Queue，并且是O(1)操作。此方法位于System.Collections命名空间下。

用法:

public virtual object Peek ();

返回值：队列开始处的对象。

异常：如果Queue为空，则此方法将提供InvalidOperationException。

以下示例程序旨在说明上述方法的使用：

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); 
    } 
}

输出：

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()); 
    } 
}

运行时错误：

Unhandled Exception:
System.InvalidOperationException: Queue empty.

参考：

https://docs.microsoft.com/en-us/dotnet/api/system.collections.queue.peek?view=netframework-4.7.2

相关用法

注：本文由纯净天空筛选整理自Kirti_Mangal大神的英文原创作品 Queue.Peek Method in C#。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。