Java LinkedTransferQueue peek()用法及代码示例

java.util.concurrent.LinkedTransferQueue.peek()方法是Java中的内置函数，如果队列为非空，则用于返回队列的头。

用法:

LinkedTransferQueue.peek()

参数：该函数不接受任何参数。

返回值：如果队列非空，则该函数返回队列的开头，否则返回null。

以下示例程序旨在说明LinkedTransferQueue.peek()方法：

示例1:

// Java Program Demonstrate peek() 
// method of LinkedTransferQueue  
  
import java.util.concurrent.LinkedTransferQueue; 
  
class LinkedTransferQueuePeekExample1 { 
    public static void main(String[] args) 
    { 
        // Initializing the queue 
        LinkedTransferQueue<Character> queue =  
                      new LinkedTransferQueue<Character>(); 
  
        // Adding elements to this queue 
        for (char ch = 'A'; ch <= 'Z'; ch++) { 
            queue.add(ch); 
        } 
  
        // Printing the head of the queue 
        System.out.println("The head of the queue is " 
                                        + queue.peek()); 
  
        // Printing all the elements of the queue 
        System.out.println("The elements in the queue :"); 
        for (Character i : queue) 
            System.out.print(i + " "); 
    } 
}

输出：

The head of the queue is A
The elements in the queue :
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

示例2:

// Java Program Demonstrate peek() 
// method of LinkedTransferQueue  
  
import java.util.concurrent.LinkedTransferQueue; 
  
class LinkedTransferQueuePeekExample2 { 
    public static void main(String[] args) 
    { 
        // Initializing the queue 
        LinkedTransferQueue<Integer> queue =  
                 new LinkedTransferQueue<Integer>(); 
  
        // Adding elements to this queue 
        for (int i = 10; i <= 50; i += 10) 
            queue.add(i); 
  
        // Printing the head of the queue 
        System.out.println("The head of the queue is " 
                                           + queue.peek()); 
  
        // Printing all the elements of the queue 
        System.out.println("The elements in the queue :"); 
        for (Integer i : queue) 
            System.out.print(i + " "); 
    } 
}

输出：

The head of the queue is 10
The elements in the queue :
10 20 30 40 50

参考： https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/LinkedTransferQueue.html#peek()

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注：本文由纯净天空筛选整理自rupesh_rao大神的英文原创作品 LinkedTransferQueue peek() method in Java。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。