public BitmapDescriptor fromCacheMarker(final CacheMarker d) {
        BitmapDescriptor bd = cache.get(d.hashCode());
        if (bd == null) {
            bd = toBitmapDescriptor(d.getDrawable());
            cache.put(d.hashCode(), bd);
        }
        return bd;
    }
rely on unique hashcode of CacheMarker
main/src/main/java/cgeo/geocaching/maps/google/v2/BitmapDescriptorCache.java