Java LinkedList poll() method
Syntax and Examples

Syntax

public E poll()

Parameters

Parameter	Description
N/A	This method doesn't accept any parameters.

Return Value

The poll() method returns:

• The first element of the list (the head) if the list is not empty.
• null if the list is empty.

Examples

Example 1: Retrieving Head from a Non-Empty List

This example demonstrates how to use poll() when the LinkedList contains elements.

import java.util.LinkedList;

public class PollExample {
    public static void main(String[] args) {
        LinkedList<String> myList = new LinkedList<>(
                "apple", "banana", "cherry"
        );

        String head = myList.poll();

        System.out.println("Head element: " + head);
        System.out.println("List after poll(): " + myList);
    }
}

Head element: apple
List after poll(): [banana, cherry]

In this example, poll() removed “apple” from the beginning of the list and assigned it to the head variable. The remaining elements are then printed.

Example 2: Handling an Empty List

This demonstrates what happens when you call poll() on an empty LinkedList. It returns null, preventing a potential exception.

import java.util.LinkedList;

public class PollEmptyList {
    public static void main(String[] args) {
        LinkedList<Integer> emptyList = new LinkedList<>();

        Integer head = emptyList.poll();

        if (head == null) {
            System.out.println("The list is empty.");
        } else {
            System.out.println("Head element: " + head);
        }
    }
}

The list is empty.

Because emptyList was initially empty, poll() returned null. The conditional statement checks for this and prints the appropriate message.

Example 3: Using poll() in a Loop

This example shows how to continuously remove elements from the head of a LinkedList until it becomes empty, demonstrating a common use case.

import java.util.LinkedList;

public class PollLoopExample {
    public static void main(String[] args) {
        LinkedList<Double> numbers = new LinkedList<>(
                3.14, 2.71, 1.618, 0.577
        );

        while (numbers != null && !numbers.isEmpty()) {
            Double firstNumber = numbers.poll();
            System.out.println("Processing: " + firstNumber);
        }
    }
}

Processing: 3.14
Processing: 2.71
Processing: 1.618
Processing: 0.577

The loop continues as long as the list is not empty. Inside the loop, poll() removes and processes each element until the list becomes empty.