ProtectCell

public class ProtectCell extends JavaPlugin {
        public void onDisable() {}
        public void onEnable() {
            PluginManager pm = this.getServer().getPluginManager();
            pm.registerEvents(new EventListener(this), this);
        }
}

public class Cell
public class EventListener implements Listener {
        public ProtectCell plugin;
        public EventListener(ProtectCell instance) {
                plugin = instance;
        }

        @EventHandler
        public void onBlockPlace(BlockPlaceEvent event){

        }
}