Trying to get back into Java, getting stuck

I have been trying to brush up on Java, which I have not been using for a while since I graduated college last year and I’m trying the calculator conundrum exercise and the final task is driving me nuts. What am I doing wrong here?

The clue in the error message is

Expecting a throwable with cause … but current throwable has no cause.

Look at the constructors for Throwable. Indeed, look at the source for the IllegalOperationExceptionn class you’re given.

The Hints offers a hint for this task.

You need to pass the cause of the exception (exception object e) as a parameter to the IllegalOperationException constructor