In this post, We will learn How to remove the first node from a Singly Linked List in Java?
Program Logic to Remove/Delete First node from Singly Linked List:
If we want to remove the first node then we need to make the second node as head and delete memory allocated for the first node.
Node<T> tempNode = head;
head = head.next;
tempNode.next = null;
Complete Source Code:
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package com.kkjavatutorials.util; import java.util.NoSuchElementException; /** * How to remove first node from a Singly Linked List in Java ? * @author KK JavaTutorials */ public class LinkedList<T> { private Node<T> head; //This internal class represents Node in Linked List private static class Node<T>{ private T data; private Node<T> next; public Node(T data) { super(); this.data = data; this.next = null; } } /** * This method insert a Node in Linked List * @param data has to insert in the List */ public void insert(T data) { Node<T> newNode = new Node<T>(data); if(head == null) { head = newNode; }else { Node<T> currentNode = head; while (currentNode.next != null) { currentNode = currentNode.next; } currentNode.next = newNode; } } /** * Removes and returns the first element from this list. * @return the first element from this list * @throws NoSuchElementException if this list is empty */ public T removeFirst() { if(head == null) { throw new NoSuchElementException("List is Empty!!"); } Node<T> tempNode = head; T result = tempNode.data; head = head.next; tempNode.next = null; return result; } /** * Method which traverse Linked List and display all data. */ public void displayLinkedList() { Node<T> currentNode = head; while(currentNode!= null) { System.out.print(currentNode.data+" "); currentNode = currentNode.next; } } public static void main(String[] args) { LinkedList<Integer> linkedList = new LinkedList<>(); linkedList.insert(10); linkedList.insert(20); linkedList.insert(30); linkedList.insert(40); linkedList.insert(50); linkedList.insert(60); System.out.println("Original LinkedList:"); linkedList.displayLinkedList(); System.out.println(); Integer removeFirst = linkedList.removeFirst(); System.out.println("After removing first Elememnt:"+removeFirst); linkedList.displayLinkedList(); } } |
Output of this Program:
Original LinkedList:
10 20 30 40 50 60
After removing first Elememnt:10
20 30 40 50 60
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