test8.14

class Rodent{
private int refcount=0;
public Rodent(){System.out.println("Rodent");}
public void addRef(){refcount++;}
public void show(){System.out.println("Reference = "+refcount);}

}

class Mouse extends Rodent{
private Rodent rodent;
public Mouse(Rodent rodent)
{System.out.println("Mouse");
this.rodent=rodent;
this.rodent.addRef();
}

}

class Hamster extends Rodent{
private Rodent rodent;
public Hamster(Rodent rodent)
{System.out.println("Hamster");
this.rodent=rodent;
this.rodent.addRef();
}

}

class Gerbil extends Rodent{
private Rodent rodent;
public Gerbil(Rodent rodent)
{System.out.println("Gerbil");
this.rodent=rodent;
this.rodent.addRef();
}

}

public class Test14 {
public static void main(String[] args) {
Rodent r=new Rodent();r.show();
Mouse m=new Mouse(r);r.show();
Hamster h=new Hamster(r);r.show();
Gerbil g=new Gerbil(r);r.show();
}

}