Java – LinkedList poll(), pollFirst() and pollLast() methods

Description

Example Programs for poll(), pollFirst() and pollLast() methods of LinkedList class.

LinkedList.poll()

Retrieves and removes the head (first element) of this list.

import java.util.LinkedList;
class LinkedListPollMethod{

  public static void main(String[] args) {

     // Create a LinkedList of Strings
     LinkedList<String> list = new LinkedList<String>();

     // Add few Elements
     list.add("Element1");
     list.add("Element2");
     list.add("Element3");
     list.add("Element4");

     // Display LinkList elements
     System.out.println("LinkedList before: "+list);

     /* poll(): Retrieves and removes the head (first element)
      * of this list.
      */
     System.out.println("Element removed: "+list.poll());

     // Displaying list elements after poll() operation
     System.out.println("LinkedList after: "+list);
  }
}

Output:

LinkedList before: [Element1, Element2, Element3, Element4]
Element removed: Element1
LinkedList after: [Element2, Element3, Element4]

LinkedList.pollFirst()

public E pollFirst(): Retrieves and removes the first element of this list, or returns null if this list is empty.

import java.util.LinkedList;
class LinkedListPollFirstDemo{

  public static void main(String[] args) {

     // Create a LinkedList of Strings
     LinkedList<String> list = new LinkedList<String>();

     // Add few Elements
     list.add("Element1");
     list.add("Element2");
     list.add("Element3");
     list.add("Element4");

     // Display LinkList elements
     System.out.println("LinkedList before: "+list);

     /* pollFirst(): Retrieves and removes the first element 
      * of this list, or returns null if this list is empty.
      */
     System.out.println("Element removed: "+list.pollFirst());

     // Display list after calling pollFirst() method
     System.out.println("LinkedList after: "+list);
  }
}

Output:

LinkedList before: [Element1, Element2, Element3, Element4]
Element removed: Element1
LinkedList after: [Element2, Element3, Element4]

LinkedList.pollLast()

public E pollLast(): Retrieves and removes the last element of this list, or returns null if this list is empty.

import java.util.LinkedList;
class LinkedListPollLastDemo{

  public static void main(String[] args) {

     // Create a LinkedList of Strings
     LinkedList<String> list = new LinkedList<String>();

     // Add few Elements
     list.add("Element1");
     list.add("Element2");
     list.add("Element3");
     list.add("Element4");

     // Display LinkList elements
     System.out.println("LinkedList before: "+list);

     /* pollFirst(): Retrieves and removes the first element 
      * of this list, or returns null if this list is empty.
      */
     System.out.println("Element removed: "+list.pollLast());

     // Display after calling pollLast() method
     System.out.println("LinkedList after: "+list);
  }
}

Output:

LinkedList before: [Element1, Element2, Element3, Element4]
Element removed: Element4
LinkedList after: [Element1, Element2, Element3]