code: @SuppressWarnings("unchecked")
      private Segment<K,V> segmentForHash(int h) {
          long u = (((h >>> segmentShift) & segmentMask) << SSHIFT) + SBASE;
          return (Segment<K,V>) UNSAFE.getObjectVolatile(segments, u);
      }
docs: Get the segment for the given hash