Please help: circular linked list nullpointerexception error

import java.util.Scanner;
import java.util.*;
import java.io.*;

public class StringNode 
{
   //attributes
   private String data;
   private StringNode link;
   //nodes counter
   int numNodes =0;
   
   Scanner kb = new Scanner(System.in);
   
   //constructor
   public StringNode(String iData, StringNode iLink)
   {
      data = iData;
      link = iLink;
   }
   
   //create empty list 
   StringNode list = null;
   
   
   
   //*********Create method: addToFrontFILI
   public void addToFrontBM(String newN)
   {
      list = new StringNode(newN, list);
      System.out.println("A node has been added to the front.");
      numNodes++;
      System.out.println("NumNodes:" +numNodes);
   }

   //---------------------Works but causes Nullpointer Exception------------
   //Create method: printLLFILI
   public void printLLBM() 
   {
      StringNode tptr = list;
      
      while(tptr.link != list)
      {
         System.out.println(tptr.data);
         tptr = tptr.link;
      }
      
      System.out.println(tptr.data);
      
   }