Why am I getting java.lang.NullPointerException while doing linked list traversal?

Question

So I am trying to make a program that uses linked list. I am getting a runtime error when I try to run it though. I am completely confused and have literally no idea on how to fix this. There is apparently something wrong with my traversal method in MyLinkedList class.

Error: Exception in thread "main" java.lang.NullPointerException at MyLinkedList.traversal(MyLinkedList.java:68) at MyLinkedListClient.main(MyLinkedListClient.java:13)

It highlights this line of code: result = temp.getElement() + "-->";

I apologize if I have asked this in a poorly written manner. My 2nd time using this website so hopefully I do not chewed out too badly >< lol Oh and sorry if my code is formatted weird, it got weird trying to get it to look like code in my post lol.

Any help is greatly appreciated.

public class MyLinkedListClient {

public static void main(String [] args) {

  MyLinkedList<String> myList = new MyLinkedList<String>();

  myList.addFirst("MSP");
  myList.addFirst("RST");
  myList.addFirst("LAX");
  myList.addFirst("PHL");


    System.out.println(myList.traversal());

    System.out.println(myList.removeFirst() + " is removed.");

  System.out.println(myList.traversal());

}

}//end of class




public class MyLinkedList<E> {

//instance variables
private Node<E> head;
//private Node<E> tail 
private int size;

//constructor
public MyLinkedList() {
head = null;
//do something with tail
size = 0;
}   

public boolean isEmpty() {
  if(head == null)
     return true;

  return false;
}

public int size() {
  return size;
}

public void addFirst (E element) {
  Node<E> temp = new Node<E>(element, null);

  //do something with tail

  if(isEmpty())
     temp.setNext(head);
  else {
     temp.setNext(head);
     head = temp;
  }
  size++;
}


public E removeFirst() throws EmptyListException {
  if(isEmpty())
     throw new EmptyListException("The list is empty.");

  Node<E> temp = head; //step 1

  head = head.getNext(); //step 2

  temp.setNext(null); //step 3

  size--;

  return temp.getElement(); //step 4
}

public String traversal() {

  if(size() == 0)
     return "Empty list.";

  Node<E> temp = head;

  String result = "Head -->";

  int i = size();

  while (i > 0) {
     result = temp.getElement() + "-->";
     temp = temp.getNext();
     i--;
  }

  return result;
}

/*
public boolean search( E element) {

}   
*/

}//end of class