Traversing through Linked List throws me a Null Pointer exception [duplicate]

Answer 1

The problem seems to be with the method insertBelow. You have the condition to keep on going until node traversal is not null:

 while(traversal!=null){
      traversal = traversal.next;
 }

When the while loop is over traversal will be pointing to null location. Then in next line:

lastLink = traversal;

Now lastLink is null and the next line:

 lastLink.next = toInsert;

is trying to access null and hence the problem of NPE. You need to fix the code by changing while loop condition as:

 while(traversal.next!=null)