doubly linked list implementation java

1class DoublyLinkedList {    
2    //A node class for doubly linked list
3    class Node{  
4        int item;  
5        Node previous;  
6        Node next;  
7   
8        public Node(int item) {  
9            this.item = item;  
10        }  
11    }  
12    //Initially, heade and tail is set to null
13    Node head, tail = null;  
14   
15    //add a node to the list  
16    public void addNode(int item) {  
17        //Create a new node  
18        Node newNode = new Node(item);  
19   
20        //if list is empty, head and tail points to newNode  
21        if(head == null) {  
22            head = tail = newNode;  
23            //head's previous will be null  
24            head.previous = null;  
25            //tail's next will be null  
26            tail.next = null;  
27        }  
28        else {  
29            //add newNode to the end of list. tail->next set to newNode  
30            tail.next = newNode;  
31            //newNode->previous set to tail  
32            newNode.previous = tail;  
33            //newNode becomes new tail  
34            tail = newNode;  
35            //tail's next point to null  
36            tail.next = null;  
37        }  
38    }  
39   
40//print all the nodes of doubly linked list  
41    public void printNodes() {  
42        //Node current will point to head  
43        Node current = head;  
44        if(head == null) {  
45            System.out.println("Doubly linked list is empty");  
46            return;  
47        }  
48        System.out.println("Nodes of doubly linked list: ");  
49        while(current != null) {  
50            //Print each node and then go to next.  
51            System.out.print(current.item + " ");  
52            current = current.next;  
53        }  
54    }  
55}
56class Main{
57    public static void main(String[] args) {  
58        //create a DoublyLinkedList object
59        DoublyLinkedList dl_List = new DoublyLinkedList();  
60        //Add nodes to the list  
61        dl_List.addNode(10);  
62        dl_List.addNode(20);  
63        dl_List.addNode(30);  
64        dl_List.addNode(40);  
65        dl_List.addNode(50);  
66   
67        //print the nodes of DoublyLinkedList  
68        dl_List.printNodes();  
69    }  
70}  
71

1//insert link at the first location
2void insertFirst(int key, int data) {
3
4   //create a link
5   struct node *link = (struct node*) malloc(sizeof(struct node));
6   link->key = key;
7   link->data = data;
8	
9   if(isEmpty()) {
10      //make it the last link
11      last = link;
12   } else {
13      //update first prev link
14      head->prev = link;
15   }
16
17   //point it to old first link
18   link->next = head;
19	
20   //point first to new first link
21   head = link;
22}