Java 中的 LinkedTransferQueue poll()方法

原文:https://www . geeksforgeeks . org/link edtransferqueue-poll-method-in-Java/

java . util . concurrent . linkedtransferqueue . poll()方法是 Java 中的内置函数,如果队列非空,则检索并移除队列头。

语法:

LinkedTransferQueue.poll()  

参数:函数不接受任何参数。

返回值:如果队列非空,函数返回队列头,否则返回 null。

下面的程序说明了 LinkedTransferQueue.poll()方法:

程序 1:

/* Java Program Demonstrate poll()
   method of LinkedTransferQueue */

import java.util.concurrent.LinkedTransferQueue;

class LinkedTransferQueuePollExample1 {
    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.poll());

        // Printing remaining 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 :
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

程序二:

/* Java Program Demonstrate poll()
   method of LinkedTransferQueue */

import java.util.concurrent.LinkedTransferQueue;

class LinkedTransferQueuePollExample2 {
    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.poll());

        // Printing remaining 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 :
20 30 40 50

参考:https://docs . Oracle . com/javase/7/docs/API/Java/util/concurrent/linkedtransferqueue . html # poll()