protected void buildIntervals(IntervalsBuilder<T> builder) {
        // go throug map and create intervals as numbers goes
        for (Iterator<Map.Entry<T, Boolean>> it = setMap.entrySet().iterator(); it.hasNext();) {
            Map.Entry<T, Boolean> object = it.next();
            // start
            if (object.getValue() && it.hasNext())  {
                Map.Entry<T, Boolean> end = it.next();
                
                builder.add(object.getKey(), end.getKey());
            }
        }
    }