Actually, you do have the source for that class, but you'll have to do some detective work to figure out which line could have caused an NPE.
However, in skimming it I see method calls on only three references: the JTable table, the MouseEvent e, and the CellEditor editor. I can't imagine the table being set to null -- this is the object the PLF handler is handling. It also seems highly unlikely that the MouseEvent is passed in null without having triggered an NPE earlier. And the editor is tested for null before calling one of its methods.
Oh, I should point out that the above code is for JDK 1.4.2. Heh, that must be it. Anyway, as I just posted in another
thread a few minutes ago, take advantage of having the
Java sources. Even when you don't have the exact line number you can usually narrow it down.
On a side note, sometimes reading the Java source code can be very entertaining. I especially like this programming gem from the above method:
I'll never tire of finding "<boolean-expr> ? true : false". It's right up there with "if ( <boolean-expr> == true )".