Minecraft Java EventListener?

Is it possible to activate or deactivate a listener in the code using a command?

Example: if I enter / activate teleporter, a PlayerJoinEvent should be activated which keeps the player in the inventory with a teleporter item when joining.

if it is deactivated nothing should happen.

Is that possible or is there even another possibility to achieve the same goal?

Hi

I would create a Boolean which is activated at '/ teleporter'.

Then you only have to query in the event whether the Boolean is true.

Thats right