abstract class MyDreamHouse{
    abstract void makeLift(Object o);
    void paintGate(Object o){
        //your painting code goes here
    }
}

abstract class HulkHouse extends MyDreamHouse{

    void buildGarrage(Object o){

    }

    abstract void attachDoors(Object o);

}

class RealHouse extends HulkHouse{

    @Override
    void attachDoors(Object o) {

    }

    @Override
    void makeLift(Object o) {

    }

}

class abstractTester{
    public static void main(String[] args){

        MyDreamHouse myHouse1; // its ok ! coz no instances is created!

        HulkHouse hulkHouse1; // its ok ! coz no instances is created!

        RealHouse realHouse1=new RealHouse();
        RealHouse realHouse2=new RealHouse();

        myHouse1=realHouse1;
        myHouse1.makeLift("Lift 1"); //calls its child realHouse1's method

        hulkHouse1=realHouse2;
        hulkHouse1.makeLift("Lift 2");

    }
}