public class BannerPortalsAPI {
    // Get the API instance
    public static BannerPortalsAPI instance ;
 
    // Register a listener
    public void registerListener (BannerPortalsListener listener )
}

public interface BannerPortalsListener {
    void handleEvent (BannerEvent bannerEvent ) ;
}

public abstract class BannerEvent {
    public boolean cancelled = false ;
}

public class AboutToTeleportEvent extends BannerEvent {
    public final Player player ;
    public final BannerPortal portal ;
    public final BannerPortal pairedPortal ;
}

public class PlaceBannerEvent extends BannerEvent {
    public final BannerPortal portal ;
}

public class BannerPortal implements ConfigurationSerializable {
    // Is banner a wall banner
    public final boolean wall ;
    // Banner block location
    public final Location blockLoc ;
    // Direction banner is facing
    public final Vector direction ;
    public final Location enterpoint ;
    public final Location exitpoint ;
}

BannerPortalsAPI. instance. registerListener ( new BannerPortalsListener ( ) {
    @Override
    public void handleEvent (BannerEvent e ) {
        if (e instanceof AboutToTeleportEvent ) {
            Bukkit. broadcastMessage ( "tp!" ) ;
            e. cancelled = true ;
        }
        if (e instanceof PlaceBannerEvent ) {
            Bukkit. broadcastMessage ( "place!" ) ;
            e. cancelled = true ;
        }
    }
} ) ;