Question

How do I create nested lists in java? so I have a factory method below which will pass a list to the constructor of the ROOM class. But I need to associate each wall with a window, So when I iterate over the list in the constructor it knows that a certain window belongs to a certain wall?.

public static Room RoomU(){
    List<Room> RoomU = new ArrayList<Room>();

    // THESE TWO SHOULD BE PAIRED AND SO ON...
    RoomU.add(new Walls(Height, Width));
    RoomU.add(new Windows(Height,Width));

    RoomU.add(new Walls(Height, Width));
    RoomU.add(new Windows(Height,Width));

    RoomU.add(new Walls(Height, Width));
    RoomU.add(new Windows(Height,Width));

    RoomU.add(new Walls(Height, Width));
    RoomU.add(new Windows(Height,Width));

    RoomU.add(new Walls(Height, Width));
    RoomU.add(new Windows(Height,Width));

    return new Room(RoomU);
}

Answer 1

What you are looking for is probably a Map, not List.

Map<Walls, Windows> myMAp = new HashMap<Walls, Windows>();
mMap.put(new Walls(1,2), new Windows(1,2));

Looking at this again, I think that maybe you should refactor some more basic thing, and have the windows object inside the walls object:

List<Walls> rooms = new ArrayList<Walls>();
rooms.add(new Walls(1,2,new Windows(1,2)));

//--- in Walls class:
Windows windows;

public Walls(int height, int width, Windows windows) {
    this.windows = windows;
    // the rest
}