Search:

On the line where the exception is thrown, add some println's to print the objects you try to access to see which one is null (from there you can backtrack to figure out the appropriate location to...

What did you try? Post the updated code

Is there a reason why you are adding your list (and list in a JScrollPane) in the actionPerformed method? Why not add it to the user interface to begin with, and just update the model from the...