clone$()$: try

Create the clone by calling super.clone.

Make the clone's head point to a new dummy head node.

Make the next and previous in the clone's dummy head node point

back to the clone's dummy head node.

Initially set size of the clone to $0.$

Iterate through this linked list, adding each element to the

clone by calling the clone's add method.

Return the clone.

catch CloneNotSupportedException

If you've done things correctly, this catch block should

never execute. But for good style throw some sort of

RuntimeException.