A Linked List is a linear data structure, in which the elements are not stored at contiguous memory locations. The elements are linked using pointers and addresses. Each element is known as a node. This article shows how to add an element to the front of LinkedList in Java.
Method 1: (Using user-defined method)
- Allocate the memory to a new node.
- Put in the element to be inserted in the allocated node.
- Make the next of the new node as the head.
- Move the head to point to the new node.
Example:
Java
// Java program to Add an Element// to the Front of LinkedList import java.io.*; class LinkedList { // head reference Node head; // Node class class Node { int data; Node next; Node(int d) { data = d; next = null; } } // Inserting node at the front public void insertfront(int data) { // Allocating and inserting the data in that node Node new_node = new Node(data); // Make the next of the newly allocated node to be // the head new_node.next = head; // Now make the head to be the newly allocated node head = new_node; } // Printing the List public void print() { Node temp = head; while (temp != null) { System.out.print(temp.data + " "); temp = temp.next; } } public static void main(String args[]) { // create a linkedlist LinkedList l = new LinkedList(); // insert elements at the front l.insertfront(6); l.insertfront(5); l.insertfront(8); l.insertfront(9); // print the linkedlist l.print(); }} |
9 8 5 6
Method 2: (Using addFirst(E e) method of LinkedList)
Declaration:
void addFirst(Object element)
Syntax:
LinkedList.addFirst(e)
Parameters: This function accepts a single parameter element as shown in the above syntax. The element specified by this parameter is appended at beginning of the list.
Return Value: This method does not return any value.
Java
// Java program to Add an Element// to the Front of LinkedList import java.util.LinkedList; class AddElementsAtTheFront { public static void main(String args[]) { // create a LinkedList LinkedList<String> list = new LinkedList<String>(); // add elements at the front list.addFirst("HI"); list.addFirst("HOW"); list.addFirst("ARE"); list.addFirst("YOU"); // print LinkedList System.out.print(list); }} |
[YOU, ARE, HOW, HI]
Method 3: (Using offerFirst(E e))
This method also inserts the specified element at the front of the list.
Declaration:
public boolean offerFirst(E e)
Syntax:
LinkedList.offerFirst(e)
Parameters: Here, e is the element to add
Return Value: This method returns true
Example:
Java
// Java program to Add an Element // to the Front of LinkedList import java.util.LinkedList; class AddingElementsAtTheFront { public static void main(String args[]) { // create a LinkedList LinkedList<String> list = new LinkedList<String>(); // add elements at the front list.offerFirst("HI"); list.offerFirst("HOW"); list.offerFirst("ARE"); list.offerFirst("YOU"); // print the LinkedList System.out.print(list); }} |
[YOU, ARE, HOW, HI]
