GUI

Hello guys, so the other day I was on a server in which they had an option in which you would write /duel *player*, after that the player that you dueled will receive a request from which he can then type /accept or /decline, if he uses /accept then a GUI comes up for both players, right click a certain item and it would open a GUI (Kind of like the menu you get when opening a chest) And had many other items in it, you choose one of them to select a PVP Kit, once you have done that you are teleported to an arena. I really need help with this one, any experts out there to help me out? I would like to implement this into my plugin, but I don't know the code for it >.<.

Thanks

 

Post some code attempt please. Ill list some things that might help you out.

ArrayLists
HashMaps
<Player>.hidePlayer(<Player>)
<Player>.showPlayer(<Player>)

 

If you need to implement it, you can consider finding such a plugin (with an api probably) and build against it
and thumbs up for what @stormneo7 said :- )