Infinite loop when trying to print LinkedList using while loop

import java.util.*;

public class testMain {
    public static void main(String[] args){
        
        myLinked a = new myLinked();
        
        a.insertAtFront(1);
        a.insertAtFront(2);
        a.insertAtFront(3);
        a.insertAtFront(4);
        a.insertAtFront(5);
        
        System.out.println(a.getFirst());
        while (a.last.data != null) {
            System.out.println(a.getNext());
        }
    }
}

idk if anyone would understand my problem base on the code i gave here, but what should i do or add in order to print all the values properly in LinkedList using while loop?

public class myLinked {
    Node first, last,current ;
   
    public myLinked(){
        
    }
    
    public void insertAtFront(Object insertItem){
        
    Node newNode = new Node(insertItem);
    if( first == null ){ 
        first = newNode;
        last = newNode;
    }else
    {
        newNode.next = first;
        first = newNode;
    }
  }
    
    public Object removeFromFront(){
        Object removeItem = null;
    if (first == null){
          return removeItem;
      }
      removeItem = first.data;
    if ( first == last){
        first = null;
        last = null;
      }else
        first = first.next;
    return removeItem;
}
    
    public void insertAtBack(Object insertItem){

    Node newNode = new Node(insertItem);
    if (first == null){ 
        first = newNode;
        last = newNode;
    }else
    {
        last.next = newNode;
        last = newNode;
    }
  }
    
    public Object removeFromBack(){
        Object removeItem = null;
      if (first == null){
          return removeItem;
      }
    removeItem = last.data;
      
      if ( first == last){
          first = null;
          last = null;
      }else
      {
          current = first;
        while (current.next != last)
            current = current.next;
            last = current;
            last.next = null;
      }
      return removeItem;
}
    
    public Object getFirst(){
        if (first == null)
            return null;
        else{
            current = first;
            return current.data;
        }
    }
    
    public Object getNext(){
        if (current == last)
            return null;
        else{
            current = current.next;
            return current.data;
        }
    }
}

So heres my "myLinked" code that Im pretty sure no error..maybe? but ill leave it here anyway

Im beginner here so ill really appreciate for you help! <3

public class Node {
    Object data;
    Node next;
    
    Node(Object obj){
        data=obj;
    }
}

my node code..theres only 3 class here that im working with