Most Effect Way to freeze player

Do a player move event and set the to location to the from location.

 

^ And store the frozen players in a Set<UUID>

 

For my SkyFreeze I did following:
On freeze command add player to list

On move:
If player is in list
> cancel

 

Use a Set not a List, they are generally faster.
Cancelling PlayerMoveEvent causes buggy behaviour occasionally, so instead use event.setTo(event.getFrom())

 

Ohh right, thanks for telling me!

Looks like I'll be having to modify my plugin when I can to do that

 

Or you could set the walk speed and flight speed to zero.

 

I agree with you. Checking every time someone moves can be heavy on the server

 

Open a gui and keep opening till unfrozen.

 

If you wish to do it this way, use the inventory close event. Spamming it doesnt help. I personally still do recommend setting walk and flight speed to 0