How to implement Linked List without using the built-in Java library?

A linked list is a dynamic data structure that consists of a sequence of nodes, where each node contains a data element and a pointer to the next node in the list. It is used in various applications, such as memory management, caching, and database indexing. In Java, there is a built-in library that provides an implementation of a linked list, but it is essential for developers to understand how to implement it without the use of the built-in Java library.

The main goal of this article is to provide an in-depth understanding of how to implement a linked list without using the built-in Java library. The article will cover the basic concepts of a linked list and its operations, including insertion, deletion, and traversal. It will also provide sample codes to help readers understand the implementation process more clearly. The readers of this article are mainly developers who want to improve their understanding and skills in data structures, and the tone of the article will be technical and informative.

Understanding the basic concepts:

In order to implement a linked list without using the built-in Java library, it is important to understand the basic concepts of a linked list and its operations.

A node is the basic building block of a linked-list, and it contains two components: data and a next pointer. The data component holds the value of the node, and the next pointer points to the next node in the list.

A singly linked list is a linked list where each node only has a next pointer, whereas a doubly linked list has both a next and a previous pointer. In this article, we will be focusing on implementing a singly linked list.

The basic operations of a linked list include insertion, deletion, and traversal. Insertion refers to adding new nodes to the list, deletion refers to removing nodes from the list, and traversal refers to traversing through the list and printing its contents.

It’s important to note that linked lists have a dynamic size and can grow or shrink as needed, unlike arrays which have a fixed size. Also, linked lists can be used in various applications such as memory management, caching, and database indexing.

Understanding the basic concepts of a linked list, its node structure, and basic operations are crucial to successfully implementing a linked list without using the built-in Java library.

Here is a diagram to understand the linked list:

+------------+    +------------+    +------------+
|     3      |    |     5      |    |     8      |
+------------+    +------------+    +------------+
  |next    |next    |next    |next 
  |pointer |pointer |pointer |pointer
  |    +------------+    +------------+
  |    |     4      |    |     6      |
  |    +------------+    +------------+
  |next    |next    |next    |
  |pointer |pointer |pointer |
  |    +------------+    +------------+
  |    |     2      |    |     7      |
  |    +------------+    +------------+
  |next    |next    |
  |pointer |pointer |
  |    +------------+
  |    |     1      |
  |    +------------+
  |next    |
  |pointer |
  |    +------------+
  |    |     9      |
  |    +------------+
  |next    |
  |pointer |
  |    null         |
  |                |
  +----------------+

The diagram represents a singly linked list with 9 nodes. Each node is represented by a rectangle and contains two components, data, and the next pointer. The data component is represented by the number inside the rectangle which holds the value of the node, and the next pointer is represented by the arrow pointing to the next node in the list.

The list starts at the head node (node 3) and ends at the tail node (node 9) with the next pointer pointing to null. The head node is the first node in the list, and the tail node is the last node in the list. The next pointer of the tail node points to null, indicating the end of the list.

It’s important to note that the nodes in the list are connected by the next pointer, and each node only points to the next node, not the previous one. This is why it’s called a singly linked list as it has only one direction.

The diagram illustrates the basic concept of a linked list and its components, it shows the nodes’ structure and how they are connected together, and how the data flows in one direction only. It also shows that the linked list has a dynamic size and can grow or shrink as needed.

Implementing the Linked List

Once we understand the basic concepts of a linked list, we can move on to implementing the linked list without using the built-in Java library.

The first step in implementing the linked list is to create a Node class. The Node class should contain two variables, data, and the next pointer. The data variable holds the value of the node, and the next pointer points to the next node in the list. Here is an example of a Node class:

class Node {
    int data;
    Node next;

    public Node(int data) {
        this.data = data;
        this.next = null;
    }
}
Java

The next step is to create a LinkedList class, which will contain the methods for inserting, deleting, and traversing the list. The LinkedList class should contain two pointers, head, and tail, which will point to the first and last nodes in the list, respectively.

The insert() method should be used to add new nodes to the list. The method should take in the data value as a parameter and create a new Node object with that value. It should then add the new Node object to the list by updating the next pointer of the previous node and the head pointer if it’s the first node.

The delete() method should be used to remove a node from the list. The method should take in the data value as a parameter and search for the node with that value in the list. It should then remove the node by updating the next pointer of the previous node and the head pointer if it’s the first node.

The traverse() method should be used to print the contents of the list. The method should start at the head node and follow the next pointers until it reaches the tail node, printing the data value of each node along the way.

Here is an example of a LinkedList class with the insert, delete, and traverse methods:

class LinkedList {
    Node head;
    Node tail;

    public void insert(int data) {
        Node newNode = new Node(data);
        if (head == null) {
            head = newNode;
            tail = newNode;
        } else {
            tail.next = newNode;
            tail = newNode;
        }
    }

    public void delete(int data) {
        Node current = head;
        Node previous = null;
        while (current != null) {
            if (current.data == data) {
                if (previous == null) {
                    head = current.next;
                } else {
                    previous.next = current.next;
                }
                break;
            }
            previous = current;
            current = current.next;
        }
    }

    public void traverse() {
        Node current = head;
        while (current != null) {
            System.out.print(current.data + " ");
            current = current.next;
        }
        System.out.println();
    }
}
Java

It’s important to understand that the sample codes are just an example of how to implement a linked list, and they can be modified or improved to suit different needs.

Implementing the linked list without using the built-in Java library is a great way to improve your understanding and skills in data structures. It will help you to understand how the linked list works, how the nodes are connected, and how the data flows.

Source Code:

To further illustrate the implementation of a linked list without using the built-in Java library, here is a sample code that shows the usage of the Node class and the LinkedList class:

public class Main {
    public static void main(String[] args) {
        LinkedList list = new LinkedList();
        list.insert(1);
        list.insert(2);
        list.insert(3);
        list.insert(4);
        list.insert(5);
        System.out.println("Original List:");
        list.traverse();
        list.delete(3);
        System.out.println("List after deletion:");
        list.traverse();
    }
}
Run Code >>

The main method creates a new LinkedList object and uses the insert() method to add 5 nodes to the list with data values of 1, 2, 3, 4, and 5. It then uses the traverse() method to print the contents of the list, which should be 1, 2, 3, 4, and 5.

Output:

Original List:
1 2 3 4 5 
List after deletion:
1 2 4 5 

The code then uses the delete() method to remove the node with a data value of 3 from the list. It then uses the traverse() method again to print the contents of the list, which should now be 1, 2, 4, and 5, showing that the node with a data value of 3 has been successfully removed.

This sample code demonstrates how to use the Node class and the LinkedList class to create and manipulate a linked list without using the built-in Java library.

It’s important to note that this sample code is just an example of how to implement a linked list, and it can be modified or improved to suit different needs.

By understanding the sample code, readers will have a better understanding of how to implement a linked list without using the built-in Java library and how to use its methods.

Conclusion:

In this article, we covered how to implement a linked list without using the built-in library. We discussed the basic concepts of a linked list, including nodes, a singly linked list, and the basic operations of insertion, deletion, and traversal. We also provided sample codes for the Node class, the LinkedList class, and the main method, illustrating how to create and manipulate a linked list.

It’s important to note that understanding how to implement a linked list without using the built-in Java library is a great way to improve your understanding and skills in data structures. It will help you to understand how the linked list works, how the nodes are connected, and how the data flows.

To further improve your understanding and skills in data structures, it’s recommended to practice implementing linked lists on your own and experimenting with different scenarios and modifications. Additionally, there are many resources available online to learn more about linked lists and other data structures.

Overall, this article aimed to provide a clear and concise understanding of how to implement a linked list without using the built-in library, and it is hoped that readers will have a better understanding of the topic after reading it.

Snehasish Konger
Snehasish Konger

Snehasish Konger is the founder of Scientyfic World. Besides that, he is doing blogging for the past 3 years and has written 300+ blogs on several platforms. He is also a front-end developer and a sketch artist.

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