@Override
        public Entry<Byte, V> next() {
            if (!hasNext()) {
                throw new NoSuchElementException();
            }

            iter.next();

            return new MapEntry(iter.entryIndex);
        }
Iterator used by the {@link Map} interface.
jraft-rheakv/rheakv-core/src/main/java/com/alipay/sofa/jraft/rhea/util/ByteObjectHashMap.java