Depp Copy of ArrayList

Hi,

I am trying to implement a clone method and one of the things in my
class that I need to clone is an ArrayList. Below is the clone method:

public Object clone()
    {
        House o = null;
        try
        {
            o = (House)super.clone();
        }
        catch(CloneNotSupportedException e)
        {
            System.out.println("Cannot clone");
        }

        o.rooms = (ArrayList<Room>)this.rooms.clone();
        for(int i=0;i<this.rooms.size();i++)
        {
            o.rooms.set(i, (Room)this.rooms.get(i).clone());
        }

        return o;
    }

the line
o.rooms = (ArrayList<Room>)this.rooms.clone();
causes a warning:
House.java:25: warning: [unchecked] unchecked cast
found : java.lang.Object
required: java.util.ArrayList<Room>
                o.rooms = (ArrayList<Room>)this.rooms.clone();

Now I realise that this is because when I clone my list the compiler
isn't sure that I have an arraylist containing the right sort of
elements, due to the use of generics. But how can I reassure the
compiler that my list DOES contain only things of type Room and get rid
of the warning?

Thanks