How to add element at first and last position of linked list in Java?

Given a Linked List in Java, the task is to insert elements at first and last position in this LinkedList.

Examples:

Input: LinkedList: [‘e’, ‘e’, ‘k’], insert at first = ‘G’, insert at last = ‘s’
Output: LinkedList: [‘G’, ‘e’, ‘e’, ‘k’, ‘s’]



Input: LinkedList: [2, 3, 4], insert at first = 1, insert at last = 5
Output: LinkedList: [1, 2, 3, 4, 5]

This can be achieved with the help of LinkedList.addFirst() and LinkedList.addLast() methods of LinkedList class in Java.

Below is the implementation of the above approach:

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// Java program to insert elements
// at first and last position in the LinkedList
  
import java.util.*;
  
public class GFG {
    public static void main(String args[])
    {
        // Creating linked list
        LinkedList<String>
            linkedList = new LinkedList<String>();
  
        // Adding elements to the linked list
        // By default elements are inserted at 
        // the last.
        linkedList.add("e");
        linkedList.add("e");
        linkedList.add("k");
        System.out.println("Linked list: "
                           + linkedList);
  
        // Inserting at first position
        linkedList.addFirst("G");
  
        // Inserting at last position
        linkedList.addLast("s");
  
        // Print the updated LinkedList
        System.out.println("Updated Linked list: "
                           + linkedList);
    }
}

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Output:

Linked list: [e, e, k]
Updated Linked list: [G, e, e, k, s]

Note : add() and addLast() provide same functionality. LinkedList implements two interfaces, Deque and Queue. It inherits add() from Deque and addLast() from Queue.



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