linked list

public class SinglyLinkedList{
class Node{
int data;
Node next;
public Node(int data){
this.data = data;
this.next=null;
} }
public Node head= null;
public Node tail= null;
public void addNode(int data){
Node newNode = new Node(data);
if(head==null){
head = newNode;
tail= newNode;
}
else{
tail.next = newNode;
tail = newNode;
}
}
public void display(){
Node current = head;
if(head==null){
System.out.println("List is empty");
return;
}
System.out.println("Nodes of singly linked list: ");
while(current!=null){
System.out.print(current.data+"");
current = current.next;
}
System.out.println();
}
public static void main(String[] args){
SinglyLinkedList sList = new SinglyLinkedList();
sList.addNode(1);
sList.addNode(2);
sList.addNode(3);
sList.addNode(4);
sList.display();
}
}