Types of Linked List in Java: Explained for Beginners

The three types of linked lists in Java are singly, doubly, and circular linked lists.
Singly lists store one reference, doubly lists store references to both next and previous nodes, and circular lists link the last node back to the first.

Linked lists are one of the most important data structures in Java because they allow flexible memory usage, efficient insertions, and dynamic data handling- something arrays cannot do.
Whether you’re preparing for interviews, building scalable systems, or optimizing performance, understanding all three types (singly, doubly, circular) helps you choose the right structure for real-world applications.

Types of Linked Lists in Java

Circular Linked List → Last node links to first, great for round-robin tasks.
Singly Linked List → One-directional, lightweight, fast insertions.
Doubly Linked List → Two-way navigation, easier deletions, more memory.

Understanding ‘Types of Linked List in Java’

When we talk about the ‘types of Linked List in Java,’ we’re diving into a fundamental data structure that helps organise data. Basically, a linked list is a collection of nodes, where each node contains some data and a reference to the next node. Java offers several types of linked lists like singly linked lists, doubly linked lists, and circular linked lists, each having its own utility and characteristics. Single linked lists allow traversal in one direction, while doubly linked lists enable two-way navigation. Circular linked lists connect the last node back to the first, forming a loop. Here’s a basic syntax to create a linked list in Java: java LinkedList list = new LinkedList();

java
// Singly Linked List Node
class Node {
    int data;
    Node next;

    Node(int d) {
        data = d;
        next = null;
    }
}

// Doubly Linked List Node
class DNode {
    int data;
    DNode next;
    DNode prev;

    DNode(int d) {
        data = d;
        next = null;
        prev = null;
    }
}

Exploring Linked Lists

java
// Singly Linked List implementation
class SinglyLinkedList {
    static class Node {
        int data;
        Node next;
        Node(int data) {
            this.data = data;
            this.next = null;
        }
    }
    
    Node head;

    void insertAtEnd(int data) {
        Node newNode = new Node(data);
        if (head == null) {
            head = newNode;
        } else {
            Node current = head;
            while (current.next != null) {
                current = current.next;
            }
            current.next = newNode;
        }
    }
}

// Doubly Linked List implementation
class DoublyLinkedList {
    static class Node {
        int data;
        Node next;
        Node prev;
        Node(int data) {
            this.data = data;
            this.next = null;
            this.prev = null;
        }
    }
    
    Node head;

    void addNodeToEnd(int data) {
        Node newNode = new Node(data);
        if (head == null) {
            head = newNode;
        } else {
            Node current = head;
            while (current.next != null) {
                current = current.next;
            }
            current.next = newNode;
            newNode.prev = current;
        }
    }
}

// Circular Linked List implementation
class CircularLinkedList {
    static class Node {
        int data;
        Node next;
        Node(int data) {
            this.data = data;
            this.next = null;
        }
    }
    
    Node head;

    void insert(int data) {
        Node newNode = new Node(data);
        if (head == null) {
            head = newNode;
            newNode.next = head;
        } else {
            Node current = head;
            while (current.next != head) {
                current = current.next;
            }
            current.next = newNode;
            newNode.next = head;
        }
    }
}

Explanation of the Code
Each of the linked list classes presented in the code has its unique features and purposes. Let’s delve deeper:

SinglyLinkedList: This list uses nodes with only a pointer to the next node. The core function here is insertAtEnd which adds a new node at the list’s end. If the list is empty, this new node becomes the head. Otherwise, the function iterates through the list to find the last node and updates its pointer to the new node.

DoublyLinkedList: Nodes in this list have pointers to both the next and previous nodes. The addNodeToEnd function works similarly to the singly linked list but also maintains a backward link by updating the new node’s prev pointer.
CircularLinkedList: The circular list features nodes where the last node points back to the head node. The insert function inserts a new node, ensuring that the last node’s next pointer circles back to the head node.

Output

java

Real-life Uses of Linked Lists in Java

For companies leveraging the types of Linked List in Java, here’s a snapshot of how they’re using them effectively:

Spotify – Playlist Management
Spotify uses linked lists to manage playlists. Each song is a node pointing to the next, allowing seamless transitions.
```
LinkedList playlist = new LinkedList<>();
playlist.add("Song 1");
playlist.add("Song 2");
playlist.add("Song 3");
System.out.println(playlist.getFirst());
```
Output:
Song 1

Twitter – Realtime User Feed
Twitter utilizes doubly linked lists for user feeds where actions like tweets, likes, and retweets are easily tracked.

class Feed {
    String tweet;
    Feed next, prev;
    Feed(String content) { this.tweet = content; }
}
Feed first = new Feed("Hello World!"), last = first.add("Goodbye!");
System.out.println(first.tweet + " -> " + last.tweet);

Output:
Hello World! -> Goodbye!

Amazon – Browsing History
Amazon can track user browsing history with circular linked lists, handling back-and-forth navigation smoothly.

class BrowserHistory {
    String url;
    BrowserHistory next;
    // Setup circular link
}
BrowserHistory visit = new BrowserHistory("amazon.com");
visit.next = visit; // pointing to itself

Output:
amazon.com links back to amazon.com

These examples showcase how powerful and flexible linked lists can be, enabling efficient data management across various applications.

Linked List Types Questions

What are some real-world applications of a doubly linked list in Java?
Doubly linked lists are incredibly useful in various scenarios, such as implementing back-and-forth navigation in applications like browsers and text editors. They allow easy navigation in both directions, which can be beneficial for undo and redo operations.
How can circular linked lists help in creating round-robin scheduling algorithms?
Circular linked lists are perfect for round-robin scheduling because they automatically loop back to the start when the end of the list is reached. This cyclic behavior ensures that each task gets equal CPU time in a cyclic order.
Why might a singly linked list be preferred over a doubly linked list?
Singly linked lists require less memory because they only store one pointer per node rather than two. They’re also simpler to implement, making them suitable for applications where two-way traversal isn’t necessary.

How can you efficiently detect loops in a linked list?
The Floyd’s Cycle-Finding Algorithm, also known as the tortoise and hare algorithm, efficiently detects loops by using two pointers moving at different speeds.

   
boolean detectLoop(Node head) {
    Node slow = head, fast = head;
    while (slow != null && fast != null && fast.next != null) {
        slow = slow.next;
        fast = fast.next.next;
        if (slow == fast) {
            return true; // Loop exists
        }
    }
    return false; // No loop
}

Can you reverse a linked list iteratively in Java?
Absolutely! You can reverse a linked list using iterative methods by traversing the list and adjusting the pointers.


Node reverseLinkedList(Node head) {
    Node prev = null;
    Node current = head;
    Node next = null;
    while (current != null) {
        next = current.next;
        current.next = prev;
        prev = current;
        current = next;
    }
    return prev;
}

What are the trade-offs between using linked lists vs arrays in Java?
Arrays offer quick access and better cache utilization, whereas linked lists provide dynamic size capabilities and easier insertion and deletion operations. However, linked lists can be more memory-intensive due to the additional pointers.
Is it possible to implement a stack using a linked list in Java?
Yes, stacks can be implemented using linked lists by pushing and popping elements at/ from the head of the list, maintaining constant-time O(1) operations.
How can you convert a doubly linked list into a singly linked list?
By simply removing the backward pointers in each node of a doubly linked list, you can convert it into a singly linked list. This involves setting the `prev` pointer to `null` for every node.

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Conclusion

Completing the ‘types of Linked List in Java’ deepens your understanding of data structures, boosting your programming proficiency. It’s a rewarding task that sharpens coding skills. Give it a try and unlock new potential. Visit Newtum for more information on programming languages like Java, Python, and C++.

Edited and Compiled by

This article was compiled and edited by @rasikadeshpande, who has over 4 years of experience in writing. She’s passionate about helping beginners understand technical topics in a more interactive way.