How to stop certain commands?

So, i want to cancel the /helpop command from essentials, and i want to have 3 new commands for it, !<message>, /. <message> and /helpop <message>. and yes, there will be no '/' for the '!' one.
Hope this was clear enough

 

Code:java

 
@EventHandler(priority = EventPriority.NORMAL)
private void blockCommandsWhenTalk(PlayerCommandPreprocessEvent event) {
Player player = event.getPlayer();
if(event.getMessage().startsWith("/")){
player.sendMessage("Can't do commands!");
event.setCancelled(true);
}
}
 

Change the startsWith to your command. or the action you want to be followed. Very basic example.

 

Im getting an error telling me that void cant be a type for blockCommandsWhenTalk?? HELP

Ok actually this doesnt work at all!

Ok it does work! But how do I prevent them from having any numbers in a /sponsor <playername> <Item ID> <amount> I want the amount to only be allowed 1

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