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 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 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 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]