gistfile1.java

public class Fireball extends GameObject implements Updatable {

	private static final int VELOCITY = 5;
	
	@NetworkData
	private Vector2D pos;
	@NetworkData
	private final Vector2D speed;
	
	@NetworkData
	private List<SomeObject> list;

        ...

}

public class Vector2D {
    public float x,y;
}