Adapter and PoE adapter on Cisco AP

First of all I want to say hello everyone and this is my first time posting on this sub and sorry for any grammar mistakes.

The other day I had a job to check why one Cisco AP wont work. When I came there I noticed that AP is getting power from PoE adapter, and also its "default" power adapter is also plugged in. Stuff there told me it was working like that for the last couple of years. My question is who gets priority, PoE or Power adapter? I thought that doing that can damage your AP, or whatever you want to supply power to.