Phantom types in Java

AirTrafficController.java

public class AirTrafficController {
    public static Plane<Landed> land(Plane<Flying> p) {
        return new Plane<Landed>(p);
    }

    public static Plane<Flying> takeOff(Plane<Landed> p) {
        return new Plane<Flying>(p);
    }

    public static void main(String[] args){
        Plane<Landed> p=Plane.newPlane();

        Plane<Flying> fly=takeOff(p);
        Plane<Landed> land=land(fly);

        //doesn't compile:
        //Plane<Landed> reallyLanded=land(land);
        //Plane<Flying> reallyFlying=takeOff(fly);

    }
}

FlightStatus.java

public interface FlightStatus {
}

Flying.java

public interface Flying extends FlightStatus{
}

Landed.java

public interface Landed extends FlightStatus {
}

Plane.java

public class Plane<Status extends FlightStatus> {

    private Plane(){
        // blah blah blah
    }

    public Plane(Plane<? extends FlightStatus > p){
        //copy whatever info we need
    }

    public static Plane<Landed> newPlane(){
        return new Plane<Landed>();
    }

}

Probably should have private constructor so Planes can't be created in any old state.

Plane<java.sql.Driver> b52 = new Plane()   // That's right.  Fly over the database, and DROP THE BOMB, Mr. death plane.

yeah, private is a good idea.
I thought also on making Status extend a common FlightStatus

There you go...