What do you think about Shock Collars?

We have a dog, it is in the backyard with 4 other dogs and it barks while it walks around. Barking from 5am until 10pm. She actually has a cage where she sleeps in at night but all the dogs wake up at 5am sometimes, sometimes later. She has food, water, attention and there's nothing there to bark at. Usually she's just walking around in circles or looking up or just around while she barks so it's not like she's barking at planes or squirrels or other dogs. I've never wanted to use a shock collar but I don't know how to train or silence mentally handicapped dogs, my own dog is extremely obedient and never barks without cause so Boo hoo, what to do? Thanks!