Why not to use base events implementing getHandlerList() for the Bukkit event API.

dont use base events.txt

A lot of plugins have some sort of BaseEvent, which looks like this:

public class BaseEvent extends Event {

	private static final HandlerList handlers = new HandlerList();

	@Override
	public HandlerList getHandlers() {
		return handlers;
	}

	public static HandlerList getHandlerList() {
		return handlers;
	}

}

Don't do this.
Doing this causes all listeners to be stored in the BaseEvent class when registered, which causes all listeners to be called
 when a subclass of BaseEvent is called, even if that listener isn't registered to listen to that event. 
Each event needs its own HanderList, you cannot have another (abstract) class do this. 
It makes sense that you're not supposed to have an abstract BaseEvent class: if this was fine, it'd have been done in 
 Bukkit's own Event class. 
The reason this issue is so common in plugins, is that it doesn't cause problems when using the (more common) @EventHandler 
 annotation in listeners. If you listen to events using your own EventExecutor, it will cause your listeners to be fired when 
 they shouldn't be.
Related issue: https://github.com/EssentialsX/Essentials/issues/3852