Nickname Issues - Code so specific players can see original name

I've created my nickname code and it works fine however I want to add a feature where specific players with a specific permission can see the players original name. I haven't a clue where to start i attempted it whereby I used Bukkit.getOnlinePlayers then if (nicked.getName() != nicked.getDisplayName()) ; but I don't know how to define the difference between the players who haven't done /nick and the players who have and how to define those players help would be much appreciated.

 

You could use essentials and it has /realname. Is there a reason you're not using it?

 

Would rather make custom one , dunno why just enjoy coding fixed it though created a system whereby it made a players name Chatcolor.MAGIC then if had specific permission make Chatcolor.WHITE