public Display findDisplayFor(Class cl) {
        // Go up through the class hierarchy for obj and see
        // if there is a display for its class or superclasses.

        if (cl == Object.class) {
            return defaultDisplay;
        }
        Display display = map.get(cl);
        if (display != null) {
            return display;
        }
        display = createDisplay(cl);
        if (display != null) {
            map.put(cl, display);
            return display;
        }
        display = findDisplayFor(cl.getSuperclass());
        map.put(cl, display);
        return display;
    }