doubly linked list implementationin java code example

Example 1: Linked List implementation

public class LinkedList {

    private Node head;
    private int length = 0;

    public LinkedList() {
        this.head = new Node(null);
    }

    public int size() {
        return length;
    }


     // Adds an element to the end of the list
    public void add(Object data)  {

        Node node = new Node(data);
        Node iterator = head;
        while (iterator.getNext() != null){
            iterator = iterator.getNext();
        }
        iterator.setNext(node);
        length++;
    }


     // Obtains an element by index
    public Object get(int index) {

        if (head.getNext() == null || index >= length){
            return null;
        }

        Node iterator = head.getNext();
        int counter = 0;

        while(counter < index){

            iterator = iterator.getNext();
            counter++;
        }
        return iterator.getData();

    }


     // Returns the index of the element in the list
    public int indexOf(Object data) {
        Node obj=head;
        for (int i = 0; i < length; i++) {
            obj = obj.getNext();
            if (obj.getData().equals(data)) {
                return i;
            }
        }
        return -1;
        //throw new Exception("Data not found");
    }


     // Removes an element from the list
    public boolean remove(Object data) {

        if (head.getNext() == null){
            return false;
        }

        Node iterator = head;

        while(iterator.getNext() != null){

            if (iterator.getNext().getData().equals(data)){
                iterator.setNext(iterator.getNext().getNext());
                length--;
                return true;
            }

            iterator = iterator.getNext();
        }

        return false;
    }

    private class Node {

        private Object data;
        private Node next;

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

        public Object getData() {
            return data;
        }

        public void setData(Object data) {
            this.data = data;
        }

        public Node getNext() {
            return next;
        }

        public void setNext(Node next) {
            this.next = next;
        }
    }

}

Example 2: double linked list java

class doublelinkedlist{  
    Node head;
    Node tail;

    static class Node{
        int data;
        Node previous;
        Node next;

        Node(int data) { this.data = data; }
    }

    public void addLink(int data) {
        Node node = new Node(data);

        if(head == null) {
            head = tail = node;
            head.previous = null;
        } else {
            tail.next = node;
            node.previous = tail;
            tail = node;
        }
        tail.next = null;
    }
}