Thread: NullPointerException with JUnit Testing

So I'm brushing up on my data structures and have been working on Linked Lists and Hashtables. The following method is from my Linked List class:

public void add(String key, Model pair){
        if(key.equals(null)|| pair.equals(null)){
            System.out.println("Nothing was added");
            //return;
        }
        else{
            Node currentNode = new Node(key, pair);
            if(isEmpty()){
                first = last = currentNode;
                first.setNextNode(currentNode);
                System.out.println(currentNode.toString() + " was added to "
                        + "position " + size+1);
            }
            else{
                last.setNextNode(currentNode);
                last = currentNode;
                System.out.println(currentNode.toString() + " was added to "
                        + "position " + size+1);
            }
            size++;
        }
    }

In the first part I want nothing to be added if either the key or pair object are null. However, in my test case I get an NullPointerException.

@Test
     public void testAdd2(){
         setUp();
         list.add("Name", null);
         assertEquals(null, list.get("Name"));
         //assertEquals(0, list.printSize());
         list.put(null, pair);
         assertEquals(null, list.get("name"));
         //assertEquals(0, list.printSize());
         tearDown();
     }

Any idea what is causing the error. I'm fairly new to JUnit also.

Thanks

Post the error, copied and pasted from just as it appears at your end.

java.lang.NullPointerException
	at test.LinkedList.add(LinkedList.java:23)
	at test.LinkedListDictionary.put(LinkedListDictionary.java:18)
	at testCases.LinkedListDictionaryTest.testAdd2(LinkedListDictionaryTest.java:51)