package com.plannaplan.abstracts; import java.util.ArrayList; import java.util.List; import com.plannaplan.interfaces.EventCreator; public abstract class EventWatcher { protected List creators; public EventWatcher() { this.creators = new ArrayList<>(); } public void attach(EventCreator creator) { this.creators.add(creator); } public void detach(EventCreator creator) { this.creators.remove(creator); } public void update() { } }