public static int combineZStarIntervals(int zStar1, int zStar2) {
        return zStar1 >>> 16 | zStar2 << 16;
    }
@return A new ZStar1 interval with boundaries [end(zStar1)+1, end(zStar2)]
predicate-search/src/main/java/com/yahoo/search/predicate/index/Interval.java