Implement singly linked list in java

Table of Contents

An example of linked list:
Let’s implement Linked List in java.

In this post, we will see how to implement singly linked list in java.
It is one of the most used data structure. In singly linked list, Node has data and pointer to next node. It does not have pointer to the previous node. Last node ‘s next points to null, so you can iterate over linked list by using this condition.
Node for linked list can be presented as below:


class Node {
 public int data;
 public Node next;

 public void displayNodeData() {
  System.out.println("{ " + data + " } ");
 }
}

class Node {

public int data;

public Node next;

public void displayNodeData() {

System.out.println("{ " + data + " } ");

}

An example of linked list:

Let’s implement Linked List in java.

Create a java file named SinglyLinkedList.java.


package org.arpit.java2blog;

class Node {
    public int data;
    public Node next;

    public void displayNodeData() {
        System.out.println("{ " + data + " } ");
    }
}

public class SinglyLinkedList {
    private Node head;

    public boolean isEmpty() {
        return (head == null);
    }

    // used to insert a node at the start of linked list
    public void insertFirst(int data) {
        Node newNode = new Node();
        newNode.data = data;
        newNode.next = head;
        head = newNode;
    }

    // used to delete node from start of linked list
    public Node deleteFirst() {
        Node temp = head;
        head = head.next;
        return temp;
    }

    // Use to delete node after particular node
    public void deleteAfter(Node after) {
        Node temp = head;
        while (temp.next != null && temp.data != after.data) {
            temp = temp.next;
        }
        if (temp.next != null)
            temp.next = temp.next.next;
    }

    // used to insert a node at the start of linked list
    public void insertLast(int data) {
        Node current = head;
        while (current.next != null) {
            current = current.next; // we'll loop until current.next is null
        }
        Node newNode = new Node();
        newNode.data = data;
        current.next = newNode;
    }

    // For printing Linked List
    public void printLinkedList() {
        System.out.println("Printing LinkedList (head --> last) ");
        Node current = head;
        while (current != null) {
            current.displayNodeData();
            current = current.next;
        }
        System.out.println();
    }
}

package org.arpit.java2blog;

class Node {

public int data;

public Node next;

public void displayNodeData() {

System.out.println("{ " + data + " } ");

}

public class SinglyLinkedList {

private Node head;

public boolean isEmpty() {

return (head == null);

}

// used to insert a node at the start of linked list

public void insertFirst(int data) {

Node newNode = new Node();

newNode.data = data;

newNode.next = head;

head = newNode;

}

// used to delete node from start of linked list

public Node deleteFirst() {

Node temp = head;

head = head.next;

return temp;

}

// Use to delete node after particular node

public void deleteAfter(Node after) {

Node temp = head;

while (temp.next != null && temp.data != after.data) {

temp = temp.next;

}

if (temp.next != null)

temp.next = temp.next.next;

}

// used to insert a node at the start of linked list

public void insertLast(int data) {

Node current = head;

while (current.next != null) {

current = current.next; // we'll loop until current.next is null

}

Node newNode = new Node();

newNode.data = data;

current.next = newNode;

}

// For printing Linked List

public void printLinkedList() {

System.out.println("Printing LinkedList (head --> last) ");

Node current = head;

while (current != null) {

current.displayNodeData();

current = current.next;

}

System.out.println();

}

Lets create Main class named LinkedListMain.java to create LinkedList.


package org.arpit.java2blog;

public class LinkedListMain {

    public static void main(String args[])
    {
        SinglyLinkedList myLinkedlist = new SinglyLinkedList();
        myLinkedlist.insertFirst(5);
        myLinkedlist.insertFirst(6);
        myLinkedlist.insertFirst(7);
        myLinkedlist.insertFirst(1);
        myLinkedlist.insertLast(2);
        // Linked list will be 
        // 2 -> 1 ->  7 -> 6 -> 5
        Node node=new Node();
        node.data=1;
        myLinkedlist.deleteAfter(node);
        // After deleting node after 1,Linked list will be 
        // 2 -> 1 -> 6 -> 5
        myLinkedlist.printLinkedList();
    }
}

package org.arpit.java2blog;

public class LinkedListMain {

public static void main(String args[])

{

SinglyLinkedList myLinkedlist = new SinglyLinkedList();

myLinkedlist.insertFirst(5);

myLinkedlist.insertFirst(6);

myLinkedlist.insertFirst(7);

myLinkedlist.insertFirst(1);

myLinkedlist.insertLast(2);

// Linked list will be

// 2 -> 1 -> 7 -> 6 -> 5

Node node=new Node();

node.data=1;

myLinkedlist.deleteAfter(node);

// After deleting node after 1,Linked list will be

// 2 -> 1 -> 6 -> 5

myLinkedlist.printLinkedList();

}

When you run above program, you will get below output:


Printing LinkedList (head --> last) 
{ 1 } 
{ 6 } 
{ 5 } 
{ 2 }

Printing LinkedList (head --> last)

{ 1 }

{ 6 }

{ 5 }

{ 2 }

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Comments

Daniel Nguyen says:

April 16, 2017 at 11:33 pm

Nice Sir Arpit ~! 🙂

Sachin says:

January 26, 2018 at 11:23 pm

Beautifully written sir. Thank you 🙂

Ravi Kant Shukla says:

November 2, 2018 at 10:14 am

Hi
good job.
Your comment before insertLast(int data) method is wrong.

Paras says:

June 8, 2019 at 3:21 am

This was the best implementation of Linked List in java I’ve seen on the internet. Thank you so much, cleared all my concepts.

Ravi Kumar says:

May 27, 2021 at 5:53 pm

This was the way I was looking up for.
Thank you so much.