Java LinkedList poll() Method

The LinkedList.poll() method in Java is used to retrieve and remove the first element of a LinkedList. This guide will cover the method’s usage, explain how it works, and provide examples to demonstrate its functionality.

Table of Contents

1. Introduction
2. poll Method Syntax
3. Examples
   • Retrieving and Removing the First Element
   • Handling Empty Lists
4. Conclusion

Introduction

The LinkedList.poll() method is a member of the LinkedList class in Java. It allows you to access and remove the first element of the LinkedList. This method is particularly useful for queue-like structures where you want to process and remove the element at the front of the queue.

poll Method Syntax

The syntax for the poll method is as follows:

public E poll()

• Returns: The first element of this list, or null if this list is empty.

Examples

Retrieving and Removing the First Element

The poll method can be used to retrieve and remove the first element of a LinkedList.

Example

import java.util.LinkedList;

public class PollExample {
    public static void main(String[] args) {
        // Creating a LinkedList of Strings
        LinkedList<String> list = new LinkedList<>();

        // Adding elements to the LinkedList
        list.add("Apple");
        list.add("Banana");
        list.add("Orange");

        // Retrieving and removing the first element using poll() method
        String firstElement = list.poll();

        // Printing the removed element and the updated LinkedList
        System.out.println("Removed element: " + firstElement);
        System.out.println("Updated LinkedList: " + list);
    }
}

Output:

Removed element: Apple
Updated LinkedList: [Banana, Orange]

Handling Empty Lists

If the LinkedList is empty, the poll method returns null.

Example

import java.util.LinkedList;

public class PollEmptyListExample {
    public static void main(String[] args) {
        // Creating an empty LinkedList of Strings
        LinkedList<String> list = new LinkedList<>();

        // Retrieving and removing the first element from an empty list
        String firstElement = list.poll();

        // Checking if the list is empty
        if (firstElement == null) {
            System.out.println("The list is empty.");
        } else {
            System.out.println("Removed element: " + firstElement);
        }
    }
}

Output:

The list is empty.

Conclusion

The LinkedList.poll() method in Java provides a way to retrieve and remove the first element of a LinkedList. By understanding how to use this method, you can efficiently manage collections of objects in your Java applications, particularly in queue-like structures. Handling the potential return value of null ensures your code remains robust and can handle empty lists gracefully.