code: @SuppressWarnings("unchecked")
      static final <K,V> HashEntry<K,V> entryAt(HashEntry<K,V>[] tab, int i) {
          return (tab == null) ? null :
              (HashEntry<K,V>) UNSAFE.getObjectVolatile
              (tab, ((long)i << TSHIFT) + TBASE);
      }
docs: Gets the ith element of given table (if nonnull) with volatile
  read semantics. Note: This is manually integrated into a few
  performance-sensitive methods to reduce call overhead.