Plugin Help Need help to check command

There will be no code here. I only need help on how to do something. Here is an example of the situation: The player activates a command, but I would like that he cant reactivate this command once it has already typed the command. It may only reactivated if he had disconnected before . How to see if a player has typed the command even if several players make this command ( check all the player )? I thought to use HashMap but I was not sure ...​

Fixed, im using ArrayList. ^^

EDIT by Moderator: merged posts, please use the edit button instead of double posting.